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B A Sullivan

Publications and source records attributed to B A Sullivan.

At least 19 recordsLinked to original sources
PubMed2006

Surface plasmon resonance investigations of human epidermal growth factor receptor 2.

This investigation utilizes surface plasmon resonance (SPR) spectroscopy to detect and quantify human epidermal growth factor receptor 2 (HER-2), an oncogene product that is over-expressed in some aggressive forms of breast cancer. Specifically, the HER-2 trans-membrane protein p185 and its extra cellular fragment p105 are analytes targeted in this work by using a gold-based biosensor slide on which an anti-HER-2 antibody has been immobilized by attachment to Protein G that is fixed to the gold film. A detection limit of > or =11 ng/mL for p185 resulted when trastuzumab was used as the anti-HER-2 antibody on the biosensor slide. Experiments with semi-purified p105 revealed that it binds weakly and reversibly to trastuzumab, therefore complicating its detection and quantification. Results of studies that reacted a 13-amino-acid peptide (PP13) from the HER-2 kinase domain with its specific antibody were critically different than p185 and p105 studies. Spectral analysis of the reflectivity at constant bulk buffer refractive index revealed a progressive negative SPR shift over time. A negative shift suggests that a loss of protein mass from the anti-PP13 antibody-Protein G biosensor is occurring. Several possibilities that may explain these negative SPR shifts are discussed.

Antibodies, Monoclonal↗
PubMed2001

Determining centromere identity: cyclical stories and forking paths.

The centromere is the genetic locus required for chromosome segregation. It is the site of spindle attachment to the chromosomes and is crucial for the transfer of genetic information between cell and organismal generations. Although the centromere was first recognized more than 120 years ago, little is known about what determines its site(s) of activity, and how it contributes to kinetochore formation and spindle attachment. Recent work in this field has supported the hypothesis that most eukaryotic centromeres are determined epigenetically rather than by primary DNA sequence. Here, we review recent studies that have elucidated the organization and functions of centromeric chromatin, and evaluate present-day models for how centromere identity and propagation are determined.

Animals↗
PubMed2000

Greater diversity of HIV-1 quasispecies in HIV-infected individuals with active tuberculosis.

OBJECTIVE: A continual increase in intrapatient HIV-1 heterogeneity is thought to contribute to evasion of host immune response and eventual progression to AIDS. Tuberculosis (TB) is diagnosed both early and late during the course of HIV-1 disease and may increase diversity of HIV-1 quasispecies by activating the HIV-1 immune response and increasing HIV-1 replication. We examined whether HIV-1 heterogeneity is altered in HIV-1-infected individuals with TB. METHODS: Blood samples were obtained from 7 HIV-1-infected patients with active TB (HIV/TB patients) and 9 HIV-1-infected patients (HIV patients) in Kampala, Uganda (CD4 counts of 0-650 cells/microl and HIV loads of 700-750,000 RNA copies/ml). The C2-C3 region of the HIV-1 envelope gene (env) was amplified by nested polymerase chain reaction (PCR) from lysed peripheral blood mononuclear cells (PBMCs) of each patient, and then subject to sequencing, clonal-quasispecies analysis and heteroduplex tracking analysis (HTA). RESULTS: HTA of env DNA fragments showed increased heterogeneity in the HIV/TB individuals compared with the HIV group. Further sequence and HTA analysis on ten individual env clones for each patient showed significantly greater HIV mutation frequencies in HIV/TB patients than in HIV patients. CONCLUSION: An increase in HIV-1 heterogeneity may be associated with a TB-mediated increase in HIV-1 replication. However, a diverse HIV-1 quasispecies population in HIV/TB patients as opposed to tight quasispecies clusters in HIV patients suggests a possible dissemination of lung-derived HIV-1 isolates from the TB-affected organ.

Adult↗
PubMed2000

Unusual chromosome architecture and behaviour at an HSR.

Amplification of sequences within mammalian chromosomes is often accompanied by the formation of homogeneously staining regions (HSRs). The arrangement of DNA sequences within such amplicons has been investigated, but little is known about the chromosome structure or behaviour of these unusual regions. We have analysed the metaphase chromosome structure of the dihydrofolate reductase (DHFR) amplicon of CHOC400 cells. The chromatin in this region contains hyperacetylated nucleosomes yet, at the same time, appears to be densely packed like heterochromatin. The region does not bind heterochromatin proteins. We show that the dense packing of the region is restricted to DNA located close to the chromosome core/scaffold. In contrast, levels of the chromosome scaffold protein topoisomerase II at HSRs are the same as those found at other euchromatic locations. Metaphase chromosome condensation of the HSR is shown to be sensitive to topoisomerase II inhibitors, and sister chromatids often appear to remain attached within the HSRs at metaphase. We suggest that these features underlie anaphase bridging and the aberrant interphase structure of the HSR. The DHFR amplicon is widely used as a model system to study mammalian DNA replication. We conclude that the higher-order chromosome structure of this amplicon is unusual and suggest that caution needs to be exercised in extrapolating data from HSRs to normal chromosomal loci.

Anaphase↗
PubMed1998

Variegated aneuploidy in two siblings: phenotype, genotype, CENP-E analysis, and literature review.

Cytogenetic studies of 2 sisters with mild microcephaly, growth deficiency, and mild errors of morphogenesis demonstrated a unique combination of multiple trisomies, most often involving chromosomes 8 and 18 either together as sole trisomies or in combination with other chromosomes. Since neither sib has phenotypic anomalies associated with trisomy 8 or 18 mosaicism, the trisomies likely did not occur during embryogenesis, but later possibly due to a predisposition for mitotic instability. To determine if the observed chromosome instability may be related to centromere function, metaphase cells were characterized by immunofluorescence of the centromere protein, CENP-E. Hybridization of CENP-E antibodies, in combination with in situ hybridization of a chromosome 8 or 18 alpha-satellite probe, showed hybridization to chromosomes 8 and 18 in both normal and aneuploid cells from each patient. These data indicate that the chromosomes in each child contain functional and active centromeres. The clinical and cytogenetic findings in these 2 individuals are compared with 7 other previously reported individuals, each of whom have similar findings. Together, these studies support the notion that a recessive mitotic mutant may be responsible for the chromosomal mosaicism and for the resulting clinical phenotype.

Centromere↗
PubMed1997

Immunolocalization of CENP-A suggests a distinct nucleosome structure at the inner kinetochore plate of active centromeres.

The trilaminar kinetochore directs the segregation of chromosomes in mitosis and meiosis. Despite its importance, the molecular architecture of this structure remains poorly understood [1]. The best known component of the kinetochore plates is CENP-C, a protein that is required for kinetochore assembly [2], but whose molecular role in kinetochore structure and function is unknown. Here we have raised for the first time monospecific antisera to CENP-A [3], a 17 kD centromere-specific histone variant that is 62% identical to the carboxy-terminal domain of histone H3 [4,5] and that resembles the yeast centromeric component CSE4 [6]. We have found by simultaneous immunofluorescence with centromere antigens of known ultrastructural location that CENP-A is concentrated in the region of the inner kinetochore plate at active centromeres. Because CENP-A was previously shown to co-purify with nucleosomes [7], our data suggest a specific nucleosomal substructure for the kinetochore. In human cells, these kinetochore-specific nucleosomes are enriched in alpha-satellite DNA [8]. However, the association of CENP-A with neocentromeres lacking detectable alpha-satellite DNA, and the lack of CENP-A association with alpha-satellite-rich inactive centromeres of dicentric chromosomes together suggest that CENP-A association with kinetochores is unlikely to be determined solely by DNA sequence recognition. We speculate that CENP-A binding could be a consequence of epigenetic tagging of mammalian centromeres.

Amino Acid Sequence↗
PubMed1997

Characterization of neo-centromeres in marker chromosomes lacking detectable alpha-satellite DNA.

Recent studies have implicated alpha-satellite DNA as an integral part of the centromere, important for the normal segregation of human chromosomes. To explore the relationship between the normal functioning centromere and alpha-satellite DNA, we have studied eight accessory marker chromosomes in which fluorescence in-situ hybridization could detect neither pancentromeric nor chromosome-specific alpha-satellite DNA. These accessory marker chromosomes were present in the majority of or all cells analyzed and appeared mitotically stable, thereby indicating the presence of a functional centromere. FISH analysis with both chromosome-specific libraries and single-copy YACs, together with microsatellite DNA studies, allowed unequivocal identification of both the origin and structure of these chromosomes. All but one of the marker chromosomes were linear mirror image duplications, and they were present along with either two additional normal chromosomes or with one normal and one deleted chromosome. Indirect immunofluorescence analysis revealed that the centromere protein CENP-B was not present on these markers; however, both CENP-C and CENP-E were present at a position defining a 'neo-centromere'. These studies provide insight into a newly defined class of marker chromosomes that lack detectable alpha-satellite DNA. At least for such marker chromosomes, alpha-satellite DNA at levels detectable by FISH appears unnecessary for chromosome segregation or for the association of CENP-C and CENP-E at a functional centromere.

Autoantigens↗
PubMed1996

Centromeres of human chromosomes.

The centromere, recognized cytologically as the primary constriction, is essential for chromosomal attachment to the spindle and for proper segregation of mitotic and meiotic chromosomes. Considerable progress has been made in identifying both DNA and protein components of the centromere and kinetochore complex in mammalian chromosomes, including definition of specific motor proteins with demonstrable functions in chromosome movement. Searches for possible environmental influences on chromosome disjunction might logically be based on known components of the segregation apparatus, both intrinsic and extrinsic to the chromosomes themselves. This article reviews available information on both DNA and protein components of the centromere of mammalian, particularly human, chromosomes and summarizes our current understanding of their role(s) in facilitating normal chromosome behavior in mitosis and meiosis.

Animals↗
PubMed1996

Evidence for structural heterogeneity from molecular cytogenetic analysis of dicentric Robertsonian translocations.

Most Robertsonian translocations are dicentric, suggesting that the location of chromosomal breaks leading to their formation occur in the acrocentric short arm. Previous cytogenetic and molecular cytogenetic studies have shown that few Robertsonian translocations retain ribosomal genes or beta-satellite DNA. Breakpoints in satellite III DNA, specifically between two chromosome 14-specific subfamilies, pTRS-47 and pTRS-63, have been indicated for most of the dicentric 14q21q and 13q14q translocations that have been studied. We have analyzed the structure of 36 dicentric translocations, using several repetitive DNA probes that localize to the acrocentric short arm. The majority of the translocations retained satellite III DNA, while others proved variable in structure. Of 10 14q21q translocations analyzed, satellite III DNA was undetected in 1; 6 retained one satellite III DNA subfamily, pTRS-47; and 3 appeared to contain two 14-specific satellite III DNA sub-families, pTRS-47 and pTRS-63. In 10/11 translocations involving chromosome 15, the presence of satellite III DNA was observed. Our results show that various regions of the acrocentric short arm, and, particularly, satellite III DNA sequences, are involved in the formation of Robertsonian translocations.

Centromere↗
PubMed1995

Application of FISH to complex chromosomal rearrangements associated with chronic myelogenous leukemia.

Identification of complex chromosomal rearrangements can be difficult, due either to the limited number and sometimes poor quality of metaphases in bone marrow preparations or to the nature of the rearrangements. Fluorescence in situ hybridization (FISH) using chromosome-specific DNA libraries in conjunction with a cosmid probe for the c-ABL oncogene was performed to substantiate the preliminary G-banded karyotypes of six patients with chronic myelogenous leukemia (CML). Our results indicate that FISH is sufficiently sensitive to detect complex and subtle rearrangements, even in bone marrow preparations with suboptimal metaphases, and can provide valuable corroborative information.

Bone Marrow↗
PubMed1995

Identification of centromeric antigens in dicentric Robertsonian translocations: CENP-C and CENP-E are necessary components of functional centromeres.

Robertsonian translocations are the most common structural dicentric rearrangements in humans. The stability of these dicentrics is attributed to the inactivation of one centromere by mechanisms which are currently unknown. The presence and amounts of centromeric proteins (CENPs) differ between the centromeres of the few dicentrics which have been studied, providing a limited understanding of the protein components necessary for centromeric function. However, CENP-C previously has been observed only at the active centromeres in two dicentric chromosomes. In the present investigation, the presence and localizations of several centromeric antigens, CENP-B, -C and -E, have been determined in 12 dicentric Robertsonian translocations. Each translocation was studied initially using in situ hybridization with alpha-satellite DNA probes to determine the active centromere. Subsequent immunofluorescence of monoclonal and polyclonal antibodies generated to various centromeric antigens demonstrated that the protein composition differs at the two centromeres of these dicentric translocations. While CENP-B was present at both active and inactive centromeres, CENP-C and -E were located at active centromeres only in the majority of translocations. These results confirm previous observations of CENP-C at active centromeres and provide the first evidence that CENP-E correlates with active centromeres as well, demonstrating that at least two specific centromeric proteins are required for human centromeric function.

Autoantigens↗
PubMed1994

Analysis of centromeric activity in Robertsonian translocations: implications for a functional acrocentric hierarchy.

Approximately 90% of human Robertsonian translocations occur between nonhomologous acrocentric chromosomes, producing dicentric elements which are stable in meiosis and mitosis, implying that one centromere is functionally inactivated or suppressed. To determine if this suppression is random, centromeric activity in 48 human dicentric Robertsonian translocations was assigned by assessment of the primary constrictions using dual color fluorescence in situ hybridization (FISH). Preferential activity/constriction of one centromere was observed in all except three different rearrangements. The activity is meiotically stable since intrafamilial consistency of a preferentially active centromere existed in members of six families. These results support evidence for nonrandom centromeric activity in humans and, more importantly, suggest a functional hierarchy in Robertsonian translocations with the chromosome 14 centromere most often active and the chromosome 15 centromere least often active.

Amniocentesis↗
PubMed1993

Clarification of subtle reciprocal rearrangements using fluorescence in situ hybridization.

Fluorescence in situ hybridization (FISH) using chromosome-specific DNA libraries as painting probes was applied in the analysis of six subtle, balanced chromosome rearrangements. Both fresh and older slides, some of which had been previously G-banded, were used to determine if FISH could identify unambiguously very small amounts of translocated material. Our results indicate that this procedure can clearly and precisely distinguish the specific components of extremely subtle translocations, in different cell types, such as leukocytes, aminocytes, and chorionic villus, and irregardless of preparation age. This ability makes FISH a valuable tool in clinical cytogenetics for the confirmation of preliminary G-banded karyotypes.

Chromosomes, Human, Pair 1↗
PubMed1993

A randomized, double-blind trial of fluorouracil plus placebo versus fluorouracil plus oral leucovorin in patients with metastatic colorectal cancer.

PURPOSE: A prospectively randomized trial was performed to determine whether the combination of fluorouracil (FU) plus leucovorin (FU-LV) administered orally is more effective than equitoxic FU for patients with metastatic colorectal cancer. PATIENTS AND METHODS: A double-blind, placebo-controlled trial design was used to eliminate observer bias. An escalating FU dosing schedule was used to achieve equal toxicity. End points were response, time to treatment failure (TTF), and eight quality-of-life (QL) parameters. A crossover arm allowed FU-treated patients to receive FU-LV combination treatment after treatment failure. RESULTS: Response rate was 32% for FU-LV versus 23% for FU (P = .15). Median TTF was 22 versus 16 weeks (P = .27). Median survival time was 44 versus 54 weeks (P = .26). QL was the same for both treatments, except for days of hospitalization, which was greater for FU-LV (P < .001). Toxicities were similar to those previously reported for FU-LV and FU alone. CONCLUSION: Oral LV-FU produces the same efficacy and toxicity pattern as has been reported for intravenous LV-FU. When FU-LV is compared with equitoxic doses of FU, there is no difference in patient outcome. These results suggest that patients with advanced disease should receive FU at doses adequate to produce toxicity.

Adenocarcinoma↗
PubMed1989

Influence of the rate of infusion on cyclosporine nephrotoxicity in the rat.

The effect of the rate of infusion of single and multiple doses of cyclosporine (CsA) on renal function was evaluated in Sprague-Dawley rats. CsA was dissolved in cremophore (Crem) or Tween 80 (Tween) and infused over consecutive 10-min periods at doses of 10, 20, 30 and 40 mg/kg. CsA-Crem and CsA-Tween produced similar and progressive changes in MAP, RBF, and RVR. By the end of the infusion, the mean values (% of control) of MAP (122 +/- 16% and 131 +/- 22%), RBF (56 +/- 11% and 66 +/- 20%), and RVR (222 +/- 38% and 232 +/- 134%) were significantly different from their respective preinfusion values. Infusion of Crem alone resulted in renal vasodilation at low doses and renal vasoconstriction at high doses. Vasoconstriction was not produced by infusion of Tween alone. In addition, animals were treated with vehicle alone (Gp 1), CsA 10 mg/kg/day by injection (Gp 2), or CsA 20 mg/kg/day by i.v. infusion over 4 hr (Gp 3), and were studied at 1 week. Systemic toxicity was greater with the 4-hr infusion as judged by an increase in MAP. The mean values of MAP were 107 +/- 8 (Gp 1), 101 +/- 13 (Gp 2), and 135 +/- 5 mm Hg (Gp 3; p less than 0.05). However, renal function was less severely affected with the 4-hr infusion. The mean values of CIn were 434 +/- 99 (Gp 1), 298 +/- 101 (Gp 2; p less than 0.05), and 425 +/- 114 microL/min/100 g BW (Gp 3); and the mean values for RBF were 2.72 +/- 0.74 (Gp 1), 2.08 +/- 0.17 (Gp 2; p less than 0.05), and 3.35 +/- 0.61 mL/min/100 g BW (Gp 3), respectively. Microangiograms showed marked abnormalities in the intrarenal perfusion pattern in the rats injected with CsA, 10 mg/kg BW. In rats infused over 4 hr with CsA, 20 mg/kg BW, the microangiographic pattern was normal. These studies demonstrate that the acute hemodynamic effects of CsA are directly related to the rate of infusion. Furthermore, the renal toxicity which follows repetitive injection of CsA can be minimized or avoided by administering CsA as a slow infusion. In addition to the total dose administered, the rate of infusion is an important determinant of nephrotoxicity.

Animals↗