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Biomedical subjects

A Golden

Publications and source records attributed to A Golden.

At least 19 recordsLinked to original sources
PubMed2003

Enhanced optical emission during Crab giant radio pulses.

We detected a correlation between optical and giant radio pulse emission from the Crab pulsar. Optical pulses coincident with the giant radio pulses were on average 3% brighter than those coincident with normal radio pulses. Combined with the lack of any other pulse profile changes, this result indicates that both the giant radio pulses and the increased optical emission are linked to an increase in the electron-positron plasma density.

Journal Article↗
PubMed2001

Exposure to arsenic and lead and neuropsychological development in Mexican children.

This cross-sectional study examined the effects of chronic exposure to lead (Pb), arsenic (AS) and undernutrition on the neuropsychological development of children. Two populations chronically exposed to either high (41 children) or low (39 children) levels of As and Pb were analyzed using the Wechsler Intelligence Scale for Children, Revised Version, for México (WISC-RM). Geometric means of urinary arsenic (AsU) and lead in blood (PbB) were 62.9+/-0.03 (microgAs/g creatinine) and 8.9+/-0.03 (microg/dl) for the exposed group and 40.2+/-0.03 (microgAs/g creatinine) and 9.7+/-0.02 (microg/dl) for the reference group. The height for age index (HAI) was used as an indicator of chronic malnutrition and sociodemographic information was obtained with a questionnaire. Lead and arsenic were measured by atomic absorption spectrophotometry. Data on full, verbal, and performance intelligence quotients (IQ) scores, long-term memory, linguistic abstraction, attention span, and visuospatial organization were obtained through the WISC-RM. After controlling for significant potential confounders verbal IQ (P<0.01) decreased with increasing concentrations of AsU. The HAI correlated positively with full-scale and performance IQ (P<0.01). Higher levels of AsU were significantly related to poorer performance on WISC-RM factors examining long-term memory and linguistic abstraction, while lower scores in WISC-RM factors measuring attention were obtained at increasing values of PbB. Our results suggest that exposure to As and chronic malnutrition could have an influence on verbal abilities and long-term memory, while Pb exposure could affect the attention process even at low levels.

Arsenic↗
PubMed2001

Amino acid substitution variants of APE1 and XRCC1 genes associated with ionizing radiation sensitivity.

Although several variants of DNA repair genes have been identified, their functional significance has not been determined. Using samples collected from 135 cancer-free women, this study evaluated whether amino acid substitution variants of DNA repair genes contribute to ionizing radiation (IR) susceptibility as measured by prolonged cell cycle G2 delay. PCR-restriction fragment length polymorphism (RFLP) assays were used to determine four genotypes: X-ray repair cross complementing group 1 (XRCC1, exon 6, C/T, 194 Arg/Trp and exon 10, G/A, 399 Arg/Gln), XRCC group 3 (XRCC3, exon 7, C/T, 241 Thr/Met) and apurinic/apyrimidinic endonuclease 1 (APE1, exon 5, T/G, 148 Asp/Glu). Fluorescence-activated cell sorter (FACS) analysis was used to measure cell cycle delay. APE1 (exon 5) genotype was significantly associated with mitotic delay (P = 0.01), with the Glu/Glu genotype having prolonged delay compared with the other two genotypes. The mitotic delay index (mean +/- SD) in women with the APE1 codon 148 Asp/Asp, Asp/Glu and Glu/Glu genotypes was 30.95 +/- 10.15 (n = 49), 30.65 +/- 10.4 (n = 60) and 39.56 +/- 13.12 (n = 21), respectively. There was a significant interaction between family history (FH) and APE1 (exon 5) genotype (P = 0.007) as well as FH and XRCC1 (exon 10) genotype (P = 0.005) in mitotic delay. Lastly, prolonged cell cycle delay was significantly associated with number of variant alleles when APE1 Asp148Glu and XRCC1 Arg399Gln genotypes were evaluated in a four-level model (chi(2) for linear trend = 10.9; P = 0.001). These results suggest that amino acid substitution variants of XRCC1 and APE1 may contribute to IR hypersensitivity.

Adult↗
PubMed2000

Metaphase to anaphase (mat) transition-defective mutants in Caenorhabditis elegans.

The metaphase to anaphase transition is a critical stage of the eukaryotic cell cycle, and, thus, it is highly regulated. Errors during this transition can lead to chromosome segregation defects and death of the organism. In genetic screens for temperature-sensitive maternal effect embryonic lethal (Mel) mutants, we have identified 32 mutants in the nematode Caenorhabditis elegans in which fertilized embryos arrest as one-cell embryos. In these mutant embryos, the oocyte chromosomes arrest in metaphase of meiosis I without transitioning to anaphase or producing polar bodies. An additional block in M phase exit is evidenced by the failure to form pronuclei and the persistence of phosphohistone H3 and MPM-2 antibody staining. Spermatocyte meiosis is also perturbed; primary spermatocytes arrest in metaphase of meiosis I and fail to produce secondary spermatocytes. Analogous mitotic defects cause M phase delays in mitotic germline proliferation. We have named this class of mutants "mat" for metaphase to anaphase transition defective. These mutants, representing six different complementation groups, all map near genes that encode subunits of the anaphase promoting complex or cyclosome, and, here, we show that one of the genes, emb-27, encodes the C. elegans CDC16 ortholog.

Alleles↗
PubMed2000

The polo-like kinase PLK-1 is required for nuclear envelope breakdown and the completion of meiosis in Caenorhabditis elegans.

The Polo-like kinases are key regulatory molecules required during the cell cycle for the successful completion of mitosis. We have cloned a C. elegans homolog of the Drosophila melanogaster polo gene (designated plk-1 for C. elegans polo-like kinase-1) and present the subcellular localization of the PLK-1 protein during the meiotic and mitotic cell cycles in C. elegans oocytes and embryos, respectively. Disruption of PLK-1 expression by RNA-mediated interference (RNAi) disrupts normal oocyte and embryonic development. Inspection of oocytes revealed a defect in nuclear envelope breakdown (NEBD) before ovulation. This defect in NEBD was also observed in oocytes that were depleted of the cyclin-dependent kinase NCC-1 (C. elegans homolog of Cdc2). The plk-1 RNAi oocytes were fertilized; however the resulting embryos were unable to separate their meiotic chromosomes or form and extrude polar bodies. These defects led to embryonic arrest as single cells. genesis 26:26-41, 2000. Published 2000 Wiley-Liss, Inc.

Amino Acid Sequence↗
PubMed2000

Cytoplasmic flow and the establishment of polarity in C. elegans 1-cell embryos.

Early Caenorhabditis elegans embryos provide an excellent model for the study of developmental processes. Development can be studied by direct observation under the light microscope and can be perturbed using laser manipulations, drug inhibitor treatments, and genetic mutants. The first division of the C. elegans embryo is asymmetric, generating two daughter cells unequal in size and developmental fate. These distinct fates are generated by the partitioning of cytoplasmic determinants during the first mitotic cell cycle. Partitioning of these determinants is thought to be driven by cytoplasmic flow. Recent studies in C. elegans in the past year have identified a number of components necessary for this flow, giving us a clearer picture of the molecular mechanisms underlying developmental asymmetry.

Animals↗
PubMed2000

Analysis of recombinant protein expression by MALDI-TOF mass spectrometry of bacterial colonies.

E. coli expressing soluble recombinant HIV antigens were analyzed directly by MALDI-TOF mass spectrometry (MS) from bacterial colonies picked from agar plates. An HIV envelope (ENV) antigen construct, penvA, was expressed in E. coli by transformation of the plasmid pPL/penvA-M. The plasmid was co-transformed into E. coli DH5 alpha cells with an equal quantity of the plasmid pKRR826, the parent vector without the penvA insert, and plated at medium density on L-agar plus ampicillin plates. A total of 24 colonies from four agar plates (six colonies per plate) were picked and transferred into 50% acetonitrile--0.1% trifluoroacetic acid aliquots for analysis by MALDI-TOF MS. The MS analysis detected 10 of 24 colonies expressing the recombinant protein; one colony expressed a mutant penvA protein; eleven of 24 colonies showed ions only from E. coli; and two of 24 colonies showed no detectable proteins. When E. coli transformed only with plasmid pPL/penvA-M were examined, all (10 of 10) colonies showed the penv insert by the MALDI-TOF MS method. The method is fast (less than 1.5 h for 24 colonies) and allows identification of colonies expressing intact or mutant proteins directly from culture plates without sample purification.

Bacteriological Techniques↗
PubMed2000

Caenorhabditis elegans contains a third polo-like kinase gene.

The Polo family of serine/threonine kinases have been implicated in cell cycle control in a number of diverse organisms. Their localization and biochemical activity suggest that they play an important role in centrosome maturation, G2-to-M phase progression, the promotion of anaphase, and cytokinesis. The Polo family of kinases is distinct from other serine/threonine kinases in that they all contain a polo-box sequence motif in their non-catalytic C-terminal domain. Recently, it was reported that two Polo-related kinases, Plc1 and Plc2, are present in C. elegans. Plc2 has diverged from Plc1 with poor homology within the polo-box sequence and only had 40% amino acid identity with Plc1. We report here the full-length cDNA sequence of another Polo-related kinase from C. elegans. The predicted protein product has greater than 70% amino acid identity with PLK-1/Plc1, and has a highly conserved polo-box domain.

Amino Acid Sequence↗
PubMed2000

Video display terminals and miscarriage.

Concern about possible reproductive effects of using video display terminals (VDTs) was stimulated by reports of clusters of adverse pregnancy outcomes among groups of women who used VDTs. Exposure to electromagnetic fields emitted from VDTs was suspected of increasing the risk of miscarriage. Ten epidemiological studies have examined associations between VDT use and miscarriage, most of which were not originally designed to examine this hypothesis and suffer from methodological limitations. We review these studies and present previously unpublished data in support of our conclusion that for most women in modern offices, work with VDTs does not increase their exposure to electromagnetic fields or increase their risk of miscarriage. The miscarriage risk for women who work at high-stress jobs or with older, high-emission VDTs (ELF > 3 mG), however, is still uncertain.

Abortion, Spontaneous↗
PubMed1999

A Caenorhabditis elegans wee1 homolog is expressed in a temporally and spatially restricted pattern during embryonic development.

A wee1 homolog, wee-1.1, is expressed in both a temporally and spatially restricted pattern during early Caenorhabditis elegans embryogenesis, and is undetectable throughout the remainder of embryogenesis. The wee-1.1 message appears to be zygotically expressed in the somatic founder cell E of the 12-cell embryo. This expression disappears when the E blastomere divides for the first time. The wee-1.1 message then appears transiently in the nuclei of the eight great-granddaughter cells of the AB somatic founder cell, just before these cells divide in the 16-cell embryo. Following this division, the wee-1.1 mRNA is no longer detectable throughout the remainder of embryogenesis. The expression of wee-1.1 in the E blastomere and in the AB progeny appears to be restricted to nuclei in prophase and metaphase of the cell cycle. Analysis of the wee-1.1 mRNA expression pattern in maternal-effect lethal mutants suggests that this expression pattern is restricted to cells of the E and AB fates in the early embryo. This mRNA expression pattern is restricted to a 10-15-min span of embryonic development and may be regulating the timing of crucial cell divisions at this early stage of development.

Amino Acid Sequence↗
PubMed1999

RNA-Mediated interference of a cdc25 homolog in Caenorhabditis elegans results in defects in the embryonic cortical membrane, meiosis, and mitosis.

The CDC25 dual-specificity phosphatase family has been shown to play a key role in cell cycle regulation. The phosphatase activity of CDC25 drives the cell cycle by removing inhibitory phosphates from cyclin-dependent kinase/cyclin complexes. Although the regulation of CDC25 phosphatase activity has been elucidated both biochemically and genetically in other systems, the role of this enzyme during development is not well understood. To examine the expression pattern and function of CDC25 in Caenorhabditis elegans, we characterized a cdc25 homolog, cdc-25.1, during early embryonic development. The CDC-25.1 protein localizes to oocytes, embryonic nuclei, and embryonic cortical membranes. When the expression of CDC-25.1 was disrupted by RNA-mediated interference, the anterior cortical membrane of fertilized eggs became very fluid during meiosis and subsequent mitotic cell cycles. Mispositioning of the meiotic spindle, defects in polar body extrusion and chromosome segregation, and abnormal cleavage furrows were also observed. We conclude that CDC-25.1 is required for a very early developmental process-the proper completion of meiosis prior to embryogenesis.

Animals↗
PubMed1999

Structural and functional characterization of an epitope in the conserved C-terminal region of HIV-1 gp120.

Through an integrated study of the reactivity of a monoclonal antibody, 803-15.6, with synthetic peptides and native recombinant HIV-1 envelope glycoprotein gp120, we have obtained structure-functional information on a region of rgp120 not yet elucidated by X-ray crystallography. mAb 803-15.6 binds with high affinity and broad cross-clade specificity to the conserved C-terminal region (amino acids 502-516) of HIV-1 rgp120. Phage display selection from a random peptide library identified the core binding motif as AXXKXRH, homologous to residues 502-508. Using quantitative binding analyses, the affinity of mAb 803-15.6 for native, monomeric recombinant gp120HXB2 (rgp120) was found to be similar to that for the synthetic gp120 peptide (502-516). Circular dichroism studies indicate that the synthetic peptide largely has a random coil conformation in solution. The results therefore suggest that the 803-15.6 epitope is fully accessible on rgp120 and that this region of rgp120 is as flexible as the synthetic peptide. Residues 502-504 are on the edge of a putative gp41 binding site that has been postulated to change conformation on CD4 binding. However, the affinity of mAb 803-15.6 for rgp120 is not affected by binding of CD4 and vice-versa. These results suggest either that the 502-504 region does not change conformation upon CD4 binding, or that recombinant gp120 does not undergo the same changes as occur in the native viral gp120-gp41 oligomer. The detailed characterization of the 803-15.6 epitope may be useful for further study of the role of the C5 region of gp120 in the viral attachment and fusion process.

Amino Acid Sequence↗
PubMed1999

The impact of laparoscopic surgery in the management of adnexal masses.

The objective of this study is to evaluate the clinical aspects of laparoscopic management of adnexal masses. The feasibility of this approach has been demonstrated, but the safe and effective use of laparoscopy for this indication requires training, technical skills and experience on the part of the laparoscopist. If used appropriately, many patients will benefit from minimally-invasive surgery. We compared clinical factors of patients having laparoscopy to those having laparotomy in a case-control study of 30 patients with adnexal masses. Oophorectomy or ovarian cystectomy was performed by laparoscopy for 20 women and by laparotomy for 10 women. Comparing the 2 groups, the most significant difference was the decrease in length of hospital stay in the laparoscopy group. There were no significant differences in operative time or intraoperative complications. Estimated blood loss was lower in the laparoscopy group, and no intraoperative complications occurred. No patient required conversion from laparoscopy to laparotomy. All patients had benign disease despite the inclusion of patients with risk factors for ovarian carcinoma. This study clearly demonstrates the clinical benefits of laparoscopic management of adnexal masses treated with oophorectomy or ovarian cystectomy.

Adnexal Diseases↗
PubMed1998

AIR-2: An Aurora/Ipl1-related protein kinase associated with chromosomes and midbody microtubules is required for polar body extrusion and cytokinesis in Caenorhabditis elegans embryos.

An emerging family of kinases related to the Drosophila Aurora and budding yeast Ipl1 proteins has been implicated in chromosome segregation and mitotic spindle formation in a number of organisms. Unlike other Aurora/Ipl1-related kinases, the Caenorhabditis elegans orthologue, AIR-2, is associated with meiotic and mitotic chromosomes. AIR-2 is initially localized to the chromosomes of the most mature prophase I-arrested oocyte residing next to the spermatheca. This localization is dependent on the presence of sperm in the spermatheca. After fertilization, AIR-2 remains associated with chromosomes during each meiotic division. However, during both meiotic anaphases, AIR-2 is present between the separating chromosomes. AIR-2 also remains associated with both extruded polar bodies. In the embryo, AIR-2 is found on metaphase chromosomes, moves to midbody microtubules at anaphase, and then persists at the cytokinesis remnant. Disruption of AIR-2 expression by RNA- mediated interference produces entire broods of one-cell embryos that have executed multiple cell cycles in the complete absence of cytokinesis. The embryos accumulate large amounts of DNA and microtubule asters. Polar bodies are not extruded, but remain in the embryo where they continue to replicate. The cytokinesis defect appears to be late in the cell cycle because transient cleavage furrows initiate at the proper location, but regress before the division is complete. Additionally, staining with a marker of midbody microtubules revealed that at least some of the components of the midbody are not well localized in the absence of AIR-2 activity. Our results suggest that during each meiotic and mitotic division, AIR-2 may coordinate the congression of metaphase chromosomes with the subsequent events of polar body extrusion and cytokinesis.

Amino Acid Sequence↗
PubMed1998

The four cdc25 genes from the nematode Caenorhabditis elegans.

During eukaryotic evolution, multicellular organisms have evolved multiple members of gene families that may display unique, partially overlapping, or redundant functions during development. More than 75% of the C. elegans genome has been sequenced, which represents approximately 95% of the coding sequences. This provides a unique opportunity to identify most, if not all, of the members of a given gene family. We have searched the C. elegans genome database for members of a key family of cell cycle regulators, the CDC25 phosphatases, and have identified four genes. The four C. elegans genes represent a larger family within a single organism than has been reported so far in Drosophila, mice and humans. An amino acid comparison revealed a high degree of similarity and identity within the phosphatase domain. This analysis also identified an expanded consensus sequence that can be used to discover new members of the CDC25 phosphatase family. However, the four C. elegans sequences display a few novel amino acid substitutions in the residues surrounding the invariant catalytic motif CX5R. These data demonstrate the value of genome database searching for identifying new members of known gene families, understanding genetic diversity, and for studying gene structure.

Amino Acid Sequence↗
PubMed1998

Effect of promoters and signal sequences on the production of secreted HIV-1 gp120 protein in the baculovirus system.

We compared insect cell production levels of secreted HIV-1 gp120 glycoprotein encoded by five different baculovirus expression constructs. Combinations consisting of one of two baculovirus promoters (very late or hybrid late/very late) and one of three different signal sequences [human tissue plasminogen activator (tpa), human placental alkaline phosphatase (pap), or baculovirus envelope glycoprotein (gp67)] were constructed. Production of secreted gp120 from these constructs was analyzed in two enzyme-linked immunosorbent assay formats, one detecting the total amount of secreted gp120 protein and the other measuring the level of "active" gp120 (as defined by the ability to bind to CD4). We found that for all of the constructs, approximately 50 to 90% of the secreted gp120 protein was active. Furthermore, our results indicated that expression from either promoter yielded comparable production of secreted protein, despite the fact that transcription from the hybrid promoter begins at an earlier time. By contrast, the signal sequence had a much greater effect on the levels of secreted gp120: the tpa leader yielded the highest level of secreted protein, followed by the gp67 and pap sequences. This result suggests that transcription is not a limiting factor in the production of secreted gp120, but rather that downstream processing of the protein is more critical. Furthermore, these results confirm the notion that the "optimal" signal sequence is protein dependent and that an insect-derived signal sequence is not optimal in all cases.

Alkaline Phosphatase↗