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Kassam Z, Brierley J, Dawson L, Lockwood G, Perkins G, Churcher K, Ringash J. Abdominal Organ Motion During Conformal Radiation. Int J Radiat Oncol Biol Phys 2005. [DOI: 10.1016/j.ijrobp.2005.07.481] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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77
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Kassam Z, Ringash J, Perkins G, Lockwood G, Churcher K, Dawson L, Brierley J. 56 Upper abdominal organ motion during conformal radiation. Radiother Oncol 2005. [DOI: 10.1016/s0167-8140(05)80217-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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78
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Hoisak J, Zheng J, Perkins G, Brock K, Allen C, Jaffray D. SU-FF-J-100: Mutual Information as a Metric of Multimodality Contrast Agent Efficacy. Med Phys 2005. [DOI: 10.1118/1.1997646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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79
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Perkins G, Mcauley D, Frank J, Thickett D, Fang X, Matthay M. Crit Care 2004; 8:P33. [DOI: 10.1186/cc2500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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80
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Huang E, Tucker S, Strom E, McNeese M, Kuerer H, Hortobagyi G, Buzdar A, Valero V, Perkins G, Hunt K, Sahin A, Buchholz T. Radiation treatment improves local-regional control and survival in patients with locally advanced breast cancer treated with neoadjuvant chemotherapy and mastectomy. Int J Radiat Oncol Biol Phys 2003. [DOI: 10.1016/s0360-3016(03)01064-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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81
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Ringash J, Perkins G, Lockwood G, Brierley J, Kim J, Wong R, Cummings B, Catton P. IMRT for adjuvant radiation in gastric cancer: a preferred plan? Int J Radiat Oncol Biol Phys 2003. [DOI: 10.1016/s0360-3016(03)01301-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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82
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Woodward W, Katz A, Buchholz T, McNeese M, Perkins G, Jhingran A, Strom E. Patterns and predictors of locoregional recurrence in 469 patients treated with post-mastecomy radiation. Int J Radiat Oncol Biol Phys 2002. [DOI: 10.1016/s0360-3016(02)03214-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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83
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Wion L, Perkins G, Ainsworth DM, Dykes NL, Divers TJ. Use of computerised tomography to diagnose a Rhodococcus equi mediastinal abscess causing severe respiratory distress in a foal. Equine Vet J 2001; 33:523-6. [PMID: 11558751 DOI: 10.2746/042516401776254736] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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84
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Desaulniers D, Leingartner K, Russo J, Perkins G, Chittim BG, Archer MC, Wade M, Yang J. Modulatory effects of neonatal exposure to TCDD, or a mixture of PCBs, p,p'-DDT, and p-p'-DDE, on methylnitrosourea-induced mammary tumor development in the rat. ENVIRONMENTAL HEALTH PERSPECTIVES 2001; 109:739-47. [PMID: 11485874 PMCID: PMC1240379 DOI: 10.1289/ehp.01109739] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The role of organochlorine (OC) exposure in the etiology of breast cancer remains controversial. Thus, our objective was to determine whether the most abundant and toxic OCs found in human milk could, when ingested during the neonatal period, modulate the development of mammary tumors in the rat. We prepared a mixture composed of p,p'-dichlorodiphenyltrichloroethane (DDT), its major metabolite, p,p'-dichlorodiphenyldichloroethene (DDE), and 19 polychlorinated biphenyls (PCB) based on their concentrations found in the milk of Canadian women. Neonate rats at 1, 5, 10, 15, and 20 days of age were gavaged with this mixture, at 10, 100, and 1,000 times the amount that a human baby would consume. An additional group received 2.5 microg 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)/kg body weight (bw) by gavage at 18 days of age, instead of the mixture. On day 21, all treatment groups, except for a control group and a 1,000-mix group, received a single intraperitoneal injection of methylnitrosourea (MNU, 30 mg/kg bw), the initiator of the carcinogenic process. The average number of rats per treatment group was 33. Rats were sacrificed when their tumors reached 1 cm in size, or at 308 days of age. We prepared mammary tumors and mammary gland whole mounts for histologic analysis. There were no significant effects when only the malignant or only the benign tumors were considered. After all benign and malignant lesions were pooled, the number of mammary tumors differed among all MNU-treated groups (p = 0.02) with more lesions developing in the MNU-1,000[times] (median = 4.5; p = 0.05) and MNU-TCDD (median = 5.5; p = 0.07) compared to the MNU-0 rats (median = 2). Compared to the MNU-0 group, the percentage of rats that developed palpable tumors (benign plus malignant) was slightly higher (p = 0.06) in the MNU-TCDD group, but not in the MNU-1,000[times] group. The percentage of palpable tumors that were malignant was higher (p = 0.02) in the MNU-100[times] group (15/16, 94%) than in the MNU-0 group (10/18, 56%). The highest dose of the mixture delayed (p = 0.03) the development of tumors, but this was not observed with the MNU-TCDD treatment. These results suggest that neonatal exposure to high doses of organochlorines could favor the development of MNU-induced mammary lesions, but also delays the development of palpable tumors in the rat.
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85
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O'Barr SA, Caguioa J, Gruol D, Perkins G, Ember JA, Hugli T, Cooper NR. Neuronal expression of a functional receptor for the C5a complement activation fragment. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2001; 166:4154-62. [PMID: 11238666 DOI: 10.4049/jimmunol.166.6.4154] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The present studies were undertaken to determine whether neuronal subsets in normal brains constitutively express functionally competent C5a receptors. In situ hybridization studies coupled with immunohistochemical approaches revealed that most neurons in the hippocampal formation, many pyramidal cortical neurons, and cerebellar Purkinje neurons in normal human and murine brains constitutively express C5a receptors. Neuronal C5a receptors bound C5a-coated fluorescent microspheres, and primary rodent hippocampal neurons responded to C5a with increased calcium fluxes via a pertussis-sensitive, presumably Gi-coupled protein. Additional studies with human neuroblastoma cells conducted to address the functional role of C5a receptors revealed that C5a triggered rapid activation of protein kinase C and activation and nuclear translocation of the NF-kappa B transcription factor. In addition, C5a was found to be mitogenic for undifferentiated human neuroblastoma cells, a novel action for the C5aR. In contrast, C5a protected terminally differentiated human neuroblastoma cells from toxicity mediated by the amyloid A beta peptide. Thus, normal rodent hippocampal neurons as well as undifferentiated and differentiated human neuroblastoma cells express functional C5a receptors. These results have implications for understanding the role of neuronal C5aR receptors in normal neuronal development, neuronal homeostasis, and neuroinflammatory conditions such as Alzheimer's disease.
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MESH Headings
- Aged
- Amyloid beta-Peptides/toxicity
- Animals
- Antigens, CD/biosynthesis
- Antigens, CD/metabolism
- Antigens, CD/physiology
- Binding Sites/immunology
- Brain Chemistry/immunology
- Calcium/metabolism
- Cell Differentiation/immunology
- Cell Survival/immunology
- Complement C5a/metabolism
- Humans
- Immunohistochemistry
- Intracellular Fluid/immunology
- Intracellular Fluid/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Transgenic
- Microscopy, Fluorescence
- Microspheres
- Nerve Growth Factors/physiology
- Neuroblastoma/immunology
- Neuroblastoma/metabolism
- Neuroblastoma/pathology
- Neurons/immunology
- Neurons/metabolism
- Neurons/physiology
- Peptide Fragments/biosynthesis
- Peptide Fragments/metabolism
- Peptide Fragments/physiology
- Receptor, Anaphylatoxin C5a
- Receptors, Complement/biosynthesis
- Receptors, Complement/metabolism
- Receptors, Complement/physiology
- Signal Transduction/immunology
- Tumor Cells, Cultured
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86
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Wang L, Sunahara RK, Krumins A, Perkins G, Crochiere ML, Mackey M, Bell S, Ellisman MH, Taylor SS. Cloning and mitochondrial localization of full-length D-AKAP2, a protein kinase A anchoring protein. Proc Natl Acad Sci U S A 2001; 98:3220-5. [PMID: 11248059 PMCID: PMC30634 DOI: 10.1073/pnas.051633398] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/29/2000] [Indexed: 01/01/2023] Open
Abstract
Differential compartmentalization of signaling molecules in cells and tissues is being recognized as an important mechanism for regulating the specificity of signal transduction pathways. A kinase anchoring proteins (AKAPs) direct the subcellular localization of protein kinase A (PKA) by binding to its regulatory (R) subunits. Dual specific AKAPs (D-AKAPs) interact with both RI and RII. A 372-residue fragment of mouse D-AKAP2 with a 40-residue C-terminal PKA binding region and a putative regulator of G protein signaling (RGS) domain was previously identified by means of a yeast two-hybrid screen. Here, we report the cloning of full-length human D-AKAP2 (662 residues) with an additional putative RGS domain, and the corresponding mouse protein less the first two exons (617 residues). Expression of D-AKAP2 was characterized by using mouse tissue extracts. Full-length D-AKAP2 from various tissues shows different molecular weights, possibly because of alternative splicing or posttranslational modifications. The cloned human gene product has a molecular weight similar to one of the prominent mouse proteins. In vivo association of D-AKAP2 with PKA in mouse brain was demonstrated by using cAMP agarose pull-down assay. Subcellular localization for endogenous mouse, rat, and human D-AKAP2 was determined by immunocytochemistry, immunohistochemistry, and tissue fractionation. D-AKAP2 from all three species is highly enriched in mitochondria. The mitochondrial localization and the presence of RGS domains in D-AKAP2 may have important implications for its function in PKA and G protein signal transduction.
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87
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O'Brien-Coker IC, Perkins G, Mallet AI. Aldehyde analysis by high performance liquid chromatography/tandem mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2001; 15:920-928. [PMID: 11400197 DOI: 10.1002/rcm.324] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
This paper describes the development of a high performance liquid chromatography/tandem mass spectrometric (MS/MS) procedure for the specific qualitative and quantitative analysis of lipid aldehydes in biological matrices. A derivatisation method, which results in molecules that exhibit a common product ion on MS/MS, permits informative precursor ion scans, at high sensitivity. This has been applied to the examination of plasma in order to examine the production of aldehydes consequent on in vitro lipid oxidation. Quantitative analysis of target molecules using multiple reaction monitoring has been developed to permit quantitation in the same matrices.
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88
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Hébert S, Perkins G, Abd el-Salam M, Caplin A. Interplay between two families of columnar defects in Bi-2212 single crystals. PHYSICA C: SUPERCONDUCTIVITY 2000; 341-348:1237-1238. [DOI: 10.1016/s0921-4534(00)01139-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
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89
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Maziak DE, Shamji F, Dennie C, Matzinger F, Perkins G. Percutaneous fine-needle aspiration biopsy for lung masses. Can J Surg 2000; 43:145-6. [PMID: 10812352 PMCID: PMC3695130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023] Open
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90
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Drury LS, Perkins G, Diffley JF. The cyclin-dependent kinase Cdc28p regulates distinct modes of Cdc6p proteolysis during the budding yeast cell cycle. Curr Biol 2000; 10:231-40. [PMID: 10712901 DOI: 10.1016/s0960-9822(00)00355-9] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
BACKGROUND Cdc28p, the major cyclin-dependent kinase in budding yeast, prevents re-replication within each cell cycle by preventing the reassembly of Cdc6p-dependent pre-replicative complexes (pre-RCs) once origins have fired. Cdc6p is a rapidly degraded protein that must be synthesised in each cell cycle and is present only during the G1 phase. RESULTS We found that, at different times in the cell cycle, there are distinct modes of Cdc6p proteolysis. Before Start, Cdc6p proteolysis did not require either the anaphase-promoting complex (APC/C) or the SCF complex, which mediate the major cell cycle regulated ubiquitination pathways, nor did it require Cdc28p activity or any of the potential Cdc28p phosphorylation sites in Cdc6p. In fact, the activation of B cyclin (Clb)-Cdc28p kinase inactivated this pathway of Cdc6p degradation later in the cell cycle. Activation of the G1 cyclins (Clns) caused Cdc6p degradation to become extremely rapid. This degradation required the SCF(CDC4) and Cdc28p consensus sites in Cdc6p, but did not require Clb5 and Clb6. Later in the cell cycle, SCF(CDC4)-dependent Cdc6p proteolysis remained active but became less rapid. CONCLUSIONS Levels of Cdc6p are regulated in several ways by the Cdc28p cyclin-dependent kinase. The Cln-dependent elimination of Cdc6p, which does not require the S-phase-promoting cyclins Clb5 and Clb6, suggests that the ability to assemble pre-RCs is lost before, not concomitant with, origin firing.
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91
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Speir JP, Perkins G, Berg C, Pullen F. Fast, generic gradient high performance liquid chromatography coupled to fourier transform ion cyclotron resonance mass spectrometry for the accurate mass analysis of mixtures. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2000; 14:1937-1942. [PMID: 11013423 DOI: 10.1002/1097-0231(20001030)14:20<1937::aid-rcm115>3.0.co;2-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Fast gradient high performance liquid chromatography (HPLC) has been combined with a commercially available Fourier transform ion cyclotron resonance (FTICR) mass spectrometer for the routine and high performance analysis of mixtures. With this combination we were able to separate and detect, under high mass accuracy conditions, a six-component drug mixture in less than 5 minutes. The fast gradients described are now possible due to the development of mechanically robust, ultra pure silica packing materials, which allow relatively high flow rates (ca. 1 mL/min for a 2 mm diameter column). For the six compounds present in the model mixture, relative mass errors of less than 1 ppm were obtained (based on an external calibration) providing sufficient mass accuracy to make unequivocal assignments of empirical formulae. Preliminary results of fast gradient HPLC/FTICR-MS/MS are also shown for the same six-component mixture. Copyright 2000 John Wiley & Sons, Ltd.
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92
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Perkins G, Ainsworth DM, Erb HN, Del Piero F, Miller M, Wilkins PA, Palmer J, Frazer M. Clinical, haematological and biochemical findings in foals with neonatal Equine herpesvirus-1 infection compared with septic and premature foals. Equine Vet J 1999; 31:422-6. [PMID: 10505959 DOI: 10.1111/j.2042-3306.1999.tb03843.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A retrospective multicentre study comparing historical, clinical, haematological, acid-base and biochemical findings of foals with Equine herpesvirus-1 (EHV-1) infection, septicaemia or prematurity was performed to determine if early diagnosis of EHV-1 foals was possible. Fifty-three foals were studied and were assigned to one of 2 groups: herpes positive (n = 14) or herpes negative (n = 39). The latter group included 20 septic, 11 premature, and 8 premature and septic foals. The presence of herpes antigen was confirmed by immunoperoxidase histochemical staining of tissues from necropsied foals. A nonparametric statistical analysis followed by a backwards elimination logistic regression was performed to establish a model at a P value of <0.05. All herpes positive foals died, while 47% (9/19) of the septic foals survived. Based upon our analysis, herpes positive foals were more likely to have total white blood cell counts less than 3 x 10(9)/l and to be icteric as compared to the septic and premature foals. Despite profound hepatic necrosis in the herpes positive foals, liver enzymes were not elevated and were not significantly different from the controls.
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93
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Perkins G, Ainsworth DM, Yeager A. Hemothorax in 2 horses. J Vet Intern Med 1999; 13:375-8. [PMID: 10449231 DOI: 10.1892/0891-6640(1999)013<0375:hih>2.3.co;2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
This report documents the successful conservative medical management of hemothorax in 2 horses. Hemothorax occurred after a lung biopsy procedure (horse 1) and strenuous exercise on a treadmill (horse 2). The horses had tachypnea, tachycardia, nostril flaring, hemoptysis, and pawing. Hemothorax was suspected based upon absence of auscultable ventral lung sounds; development of cool extremities and pale, tacky mucous membranes; the ultrasonographic appearance of moderate to severe amounts of pleural fluid; and a concurrent decrease in hematocrit and total plasma protein. Both horses were treated successfully by intranasal administration of oxygen, intravenous administration of balanced polyionic solutions, and treatment with antibiotics, nonsteroidal anti-inflammatory drugs, and analgesics. In neither case was pleural blood removed. The hemothorax resolved in both horses without lasting abnormalities. Hemothorax does not require drainage for successful resolution.
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94
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Perkins G, Pullen F, Thompson C. Automated high resolution mass spectrometry for the synthetic chemist. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 1999; 10:546-551. [PMID: 27518048 DOI: 10.1016/s1044-0305(99)00014-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/1998] [Revised: 01/22/1999] [Accepted: 02/08/1999] [Indexed: 06/06/2023]
Abstract
Exact mass measurement at high resolution is an important tool alongside other spectroscopic methods to help confirm the structure of a novel compound prepared by the synthetic chemist. Exact mass measurement is used in the pharmaceutical industry to confirm the expected empirical formula of a product when problems have been experienced using elemental analysis. Because of the amount of manual intervention necessary when acquiring exact mass measurements, especially when using probe ionization techniques such as fast atom bombardment ionization or electron ionization, this method has been seen to be time consuming and labor intensive for the mass spectrometrist. An automated high resolution mass spectrometric method has been developed at Pfizer Central Research which has streamlined exact mass measurement. The method, which uses electrospray ionization on a double focusing mass spectrometer, is described. The samples are analyzed using a flow injection technique, with sodiated polyethylene glycol present in the mobile phase to provide mass reference peaks. The data are acquired and processed using a macro developed "in house." This automated technique can process 15-20 samples an hour including data processing and report generation, using very small amounts of compound (∼25 µg), but more importantly it can be left to run unattended overnight. This allows the instrument to be used for more complex experiments during the day when it is important to have a mass spectrometrist present. The results presented here demonstrate that this method gives exact mass measurements within an acceptable limit of 5 ppm, and the variation on one sample, injected 10 times, is not excessively high (-1.8 to +1.6 mDa).
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95
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Huang LJ, Wang L, Ma Y, Durick K, Perkins G, Deerinck TJ, Ellisman MH, Taylor SS. NH2-Terminal targeting motifs direct dual specificity A-kinase-anchoring protein 1 (D-AKAP1) to either mitochondria or endoplasmic reticulum. J Cell Biol 1999; 145:951-9. [PMID: 10352013 PMCID: PMC2133123 DOI: 10.1083/jcb.145.5.951] [Citation(s) in RCA: 139] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Subcellular localization directed by specific targeting motifs is an emerging theme for regulating signal transduction pathways. For cAMP-dependent protein kinase (PKA), this is achieved primarily by its association with A-kinase-anchoring proteins (AKAPs). Dual specificity AKAP1, (D-AKAP1) binds to both type I and type II regulatory subunits and has two NH2-terminal (N0 and N1) and two COOH-terminal (C1 and C2) splice variants (. J. Biol. Chem. 272:8057). Here we report that the splice variants of D-AKAP1 are expressed in a tissue-specific manner with the NH2-terminal motifs serving as switches to localize D-AKAP1 at different sites. Northern blots showed that the N1 splice is expressed primarily in liver, while the C1 splice is predominant in testis. The C2 splice shows a general expression pattern. Microinjecting expression constructs of D-AKAP1(N0) epitope-tagged at either the NH2 or the COOH terminus showed their localization to the mitochondria based on immunocytochemistry. Deletion of N0(1-30) abolished mitochondrial targeting while N0(1-30)-GFP localized to mitochondria. Residues 1-30 of N0 are therefore necessary and sufficient for mitochondria targeting. Addition of the 33 residues of N1 targets D-AKAP1 to the ER and residues 1-63 fused to GFP are necessary and sufficient for ER targeting. Residues 14-33 of N1 are especially important for targeting to ER; however, residues 1-33 alone fused to GFP gave a diffuse distribution. N1(14-33) thus serves two functions: (a) it suppresses the mitochondrial-targeting motif located within residues 1-30 of N0 and (b) it exposes an ER-targeting motif that is at least partially contained within the N0(1-30) motif. This represents the first example of a differentially targeted AKAP and adds an additional level of complexity to the PKA signaling network.
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96
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Perkins G, Hulme J, Shore H, Bion J. Cardiopulmonary resuscitation training. JOURNAL OF THE ROYAL COLLEGE OF PHYSICIANS OF LONDON 1999; 33:193. [PMID: 10340276 PMCID: PMC9665675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
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97
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Desdouets C, Santocanale C, Drury LS, Perkins G, Foiani M, Plevani P, Diffley JF. Evidence for a Cdc6p-independent mitotic resetting event involving DNA polymerase alpha. EMBO J 1998; 17:4139-46. [PMID: 9670028 PMCID: PMC1170746 DOI: 10.1093/emboj/17.14.4139] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Eukaryotic DNA replication is limited to once per cell cycle because cyclin-dependent kinases (cdks), which are required to fire origins, also prevent re-replication. Components of the replication apparatus, therefore, are 'reset' by cdk inactivation at the end of mitosis. In budding yeast, assembly of Cdc6p-dependent pre-replicative complexes (pre-RCs) at origins can only occur during G1 because it is blocked by cdk1 (Cdc28) together with B cyclins (Clbs). Here we describe a second, separate process which is also blocked by Cdc28/Clb kinase and, therefore, can only occur during G1; the recruitment of DNA polymerase alpha-primase (pol alpha) to chromatin. The recruitment of pol alpha to chromatin during G1 is independent of pre-RC formation since it can occur in the absence of Cdc6 protein. Paradoxically, overproduction of Cdc6p can drive both dephosphorylation and chromatin association of pol alpha. Overproduction of a mutant in which the N-terminus of Cdc6 has been deleted is unable to drive pol alpha chromatin binding. Since this mutant is still competent for pre-RC formation and DNA replication, we suggest that Cdc6p overproduction resets pol alpha chromatin binding by a mechanism which is independent of that used in pre-RC assembly.
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98
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Perkins G, Diffley JF. Nucleotide-dependent prereplicative complex assembly by Cdc6p, a homolog of eukaryotic and prokaryotic clamp-loaders. Mol Cell 1998; 2:23-32. [PMID: 9702188 DOI: 10.1016/s1097-2765(00)80110-0] [Citation(s) in RCA: 163] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Expression of the Cdc6 protein (Cdc6p) is essential for formation of prereplicative complexes at budding yeast replication origins. Analysis of mutations in the conserved nucleoside triphosphate (NTP)-binding site of Cdc6p described here suggests that NTPs are required both for the productive interaction of Cdc6p with replication origins during G1 and the quantitative loading of the Mcm2-7 family of proteins onto chromatin. We show that Cdc6p exhibits significant sequence similarity to subunits of eukaryotic and prokaryotic clamp-loaders, which load ring-shaped DNA polymerase processivity factors onto DNA in an analogous reaction. Similarities in both sequence and mechanism suggest that Cdc6p and the clamp-loaders are members of a superfamily of nucleotide-dependent loading factors.
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99
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Perkins G, Valberg SJ, Madigan JM, Carlson GP, Jones SL. Electrolyte disturbances in foals with severe rhabdomyolysis. J Vet Intern Med 1998; 12:173-7. [PMID: 9595379 DOI: 10.1111/j.1939-1676.1998.tb02114.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Marked electrolyte abnormalities characterized by profound hyperkalemia, hyponatremia, hypocalcemia, and hyperphosphatemia were noted in 4 neonatal foals with acute rhabdomyolysis and pigmenturia. In 2 foals, rhabdomyolysis developed 4-6 days after admission for dysmaturity, and in 2 foals, rhabdomyolysis was evident on presentation. Rhabdomyolysis was a consequence of selenium deficiency with or without vitamin E deficiency, possibly combined with increased oxidant stress due to sepsis or hypoxia and reperfusion injury after parturition. Foals gained from 7 to 15% of their initial body weight within 48 hours of developing rhabdomyolysis. Three of the foals developed cardiac arrhythmias characterized by spiked T waves and decreased-amplitude P waves. Postmortem examination of 2 foals revealed extensive myodegeneration and renal tubular nephrosis; renal cortical necrosis with myocardial necrosis was noted in 1 foal. Destruction of the major intracellular compartment (intracellular fluid [ICF]) through extensive myonecrosis combined, in some cases, with myoglobinuric renal insufficiency produced major fluid shifts and life-threatening electrolyte derangements. With the major ICF compartment disrupted, hyperkalemia was most effectively treated using mineralocorticoids, loop diuretics, and ion exchange resins to enhance elimination. In addition, i.v. calcium, glucose, insulin, and sodium bicarbonate were administered, which helped redistribute potassium to the ICF. Severe rhabdomyolysis should be included in the differential diagnoses of hyperkalemia, hyponatremia, hypocalcemia, and hyperphosphatemia in neonatal foals.
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Ruiz-Lozano P, Smith SM, Perkins G, Kubalak SW, Boss GR, Sucov HM, Evans RM, Chien KR. Energy deprivation and a deficiency in downstream metabolic target genes during the onset of embryonic heart failure in RXRalpha−/− embryos. Development 1998; 125:533-44. [PMID: 9425147 DOI: 10.1242/dev.125.3.533] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
RXRalpha null mutant mice display ocular and cardiac malformations, liver developmental delay, and die from cardiac failure around embryonic day (E) 14.5 pc. To dissect the molecular basis of the RXRalpha-associated cardiomyopathy, we performed subtractive hybridization and systematically characterized putative downstream target genes that were selectively lacking in the mutant embryos, both at early (E10.5) and late (E13.5) stages of mouse embryonic development. Approximately 50% of the subtracted clones (61/115) encoded proteins involved in intermediary metabolism and electron transport, suggesting an energy deficiency in the RXRalpha−/− embryos. In particular, clone G1, which encodes subunit 14.5b of the NADH-ubiquinone dehydrogenase complex, displayed a dose-dependent expression in the wild-type, heterozygous and RXRalpha mutant mice. This gene was also downregulated in a retinoid-deficient rat embryo model. ATP content and medium Acyl-CoA dehydrogenase mRNA were lower in RXRalpha mutant hearts compared to wild-type mice. Ultrastructural studies showed that the density of mitochondria per myocyte was higher in the RXRalpha mutant compared to wild-type littermates. We propose a model whereby defects in intermediary metabolism may be a causative factor of the RXRalpha−/− phenotype and resembles an embryonic form of dilated cardiomyopathy.
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MESH Headings
- Acyl-CoA Dehydrogenase
- Acyl-CoA Dehydrogenases/genetics
- Adenosine Triphosphate/analysis
- Animals
- Cardiomyopathy, Dilated/embryology
- Cardiomyopathy, Dilated/genetics
- Cloning, Molecular/methods
- DNA, Complementary/genetics
- Electron Transport Complex I
- Energy Metabolism/genetics
- Gene Expression Regulation, Developmental
- Gene Library
- Genes/genetics
- Genes/physiology
- Heart/embryology
- Mice
- Mice, Knockout
- Mitochondria, Heart
- Myocardium/chemistry
- Myocardium/cytology
- Myocardium/metabolism
- Myocardium/ultrastructure
- NADH, NADPH Oxidoreductases/genetics
- RNA, Messenger/analysis
- Rats
- Rats, Mutant Strains
- Receptors, Retinoic Acid/genetics
- Receptors, Retinoic Acid/physiology
- Retinoid X Receptors
- Retinoids
- Transcription Factors/genetics
- Transcription Factors/physiology
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