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Jones MD, Ortiz G, Ceperley DM. Hartree-Fock studies of atoms in strong magnetic fields. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1996; 54:219-231. [PMID: 9913472 DOI: 10.1103/physreva.54.219] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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77
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Jones MD, Ceperley DM. Crystallization of the one-component plasma at finite temperature. PHYSICAL REVIEW LETTERS 1996; 76:4572-4575. [PMID: 10061325 DOI: 10.1103/physrevlett.76.4572] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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78
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Jones MD, Narhi LO, Chang WC, Lu HS. Refolding and oxidation of recombinant human stem cell factor produced in Escherichia coli. J Biol Chem 1996; 271:11301-8. [PMID: 8626682 DOI: 10.1074/jbc.271.19.11301] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Oxidative folding of recombinant human stem cell factor (rhSCF) produced in Escherichia coli was investigated in vitro. Folding of denatured and reduced rhSCF involves at least five intermediate forms, I-1 to I-5, detectable by their differences in hydrophobicity using reverse-phase high performance liquid chromatography. Both I-1 and I-2 contain a native-like disulfide bond, Cys4-Cys89 and Cys43-Cys138, respectively, and I-3 forms a mispaired disulfide, Cys43-Cys89. These forms appear to reach steady state equilibrium and are important folding intermediates. I-1 was found to be the prominent intermediate that directly folds into native rhSCF (N); and the thermodynamically less stable I-2 favors rearrangment into I-1. I-3 may serve as an intermediate for disulfide rearrangment between I-1 and I-2. I-4 and I-5, which are disulfide-linked dimers, are in equilibrium with reduced rhSCF and other intermediates and may not play an important role in rhSCF folding. Both trifluoroacetic acid-trapped I-1 and I-2, after isolation by high performance liquid chromatography, proceed with the remaining oxidative folding process after reconstitution. Iodoacetate-trapped I-1 and I-2 contain low alpha-helical content and some tertiary structure, while I-3 and reduced rhSCF have little ordered structure. Gel filtration/light-scattering experiments indicate that reduced rhSCF and iodoacetate-trapped I-1, I-2, and I-3 exist as dimeric forms, indicating that rhSCF dimerization precedes formation of disulfide bonds. I-1, I-2, I-3, and the C43,138A analog lacking Cys43-Cys138 bond are not biologically active or exhibit significantly lower activity. The two disulfide bonds in rhSCF seem to be essential for the molecule to maintain an active conformation required for its receptor binding and biological activities.
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MESH Headings
- Amino Acid Sequence
- Chromatography, Gel
- Chromatography, High Pressure Liquid
- Circular Dichroism
- Cloning, Molecular
- Cysteine
- Disulfides
- Electrophoresis, Polyacrylamide Gel
- Escherichia coli
- Humans
- Iodoacetates
- Iodoacetic Acid
- Kinetics
- Light
- Mutagenesis, Site-Directed
- Oxidation-Reduction
- Peptide Fragments/chemistry
- Peptide Fragments/isolation & purification
- Peptide Mapping
- Point Mutation
- Protein Denaturation
- Protein Folding
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Recombinant Proteins/chemistry
- Recombinant Proteins/isolation & purification
- Recombinant Proteins/metabolism
- Scattering, Radiation
- Spectrometry, Fluorescence
- Spectrophotometry, Ultraviolet
- Stem Cell Factor/chemistry
- Stem Cell Factor/isolation & purification
- Stem Cell Factor/metabolism
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Lu HS, Jones MD, Shieh JH, Mendiaz EA, Feng D, Watler P, Narhi LO, Langley KE. Isolation and characterization of a disulfide-linked human stem cell factor dimer. Biochemical, biophysical, and biological comparison to the noncovalently held dimer. J Biol Chem 1996; 271:11309-16. [PMID: 8626683 DOI: 10.1074/jbc.271.19.11309] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Distinct from the noncovalently linked recombinant human stem call factor (rhSCF) dimer, we report here the isolation and identification of an SDS-nondissociable dimer produced during folding/oxidation of rhSCF. Experimental evidence using various cleavage strategies and analyses shows that the isolated dimer is composed of two rhSCF monomers covalently linked by four disulfide bonds. The cysteines are paired as in the noncovalently associated dimer except that all pairings are intermolecular rather than intramolecular. Other structural models, involving intertwining of intramolecular disulfide loops, are ruled out. The molecule behaves similarly to the noncovalently associated dimer during ion-exchange or gel permeation chromatography. However, the disulfide-linked dimer exhibits increased hydrophobicity in reverse-phase columns and in the native state does not undergo spontaneous dimer dissociation-association as seen for the noncovalent dimer. Spectroscopic analyses indicate that the disulfide-linked and noncovalently associated rhSCF dimers have grossly similar secondary and tertiary structures. In vitro, the disulfide-linked dimer exhibits approximately 3-fold higher biological activity in supporting growth of a hematopoietic cell line and stimulating hematopoietic cell colony formation from enriched human CD34+ cells. The molecule binds to the rhSCF receptor, Kit, with an efficiency only half that of the noncovalently associated dimer. Formation of intermolecular disulfides in the disulfide-linked dimer with retention of biological activity has implications for the three-dimensional structure of noncovalently held dimer and disulfide-linked dimer.
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80
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Jones MD, James WS, Barasi S, Nokes LD. Postmortem electrical excitability of skeletal muscle: preliminary investigation of an animal model. Forensic Sci Int 1995; 76:91-6. [PMID: 8566916 DOI: 10.1016/0379-0738(95)01802-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Presented is a preliminary study of the feasibility of using an animal model to investigate the postmortem time-dependent decay in muscular response, when subjected to electrical stimulation and to develop an animal model for the assessment of the use of electrical excitability as a method for determining the postmortem period of a human corpse. Analysis of the results shows a correlation between the rate of decay of muscular response with the postmortem interval.
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81
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Ortiz G, Jones MD, Ceperley DM. Ground state of a hydrogen molecule in superstrong magnetic fields. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1995; 52:R3405-R3408. [PMID: 9912761 DOI: 10.1103/physreva.52.r3405] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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82
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Turbow RM, Curran-Everett D, Hay WW, Jones MD. Cerebral lactate metabolism in near-term fetal sheep. THE AMERICAN JOURNAL OF PHYSIOLOGY 1995; 269:R938-42. [PMID: 7485614 DOI: 10.1152/ajpregu.1995.269.4.r938] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The present study was designed to see if lactate can cross the blood-brain barrier of the near-term fetal sheep and replace glucose as an oxidative substrate during normoglycemia and acute insulin-induced hypoglycemia. Cerebral uptake of glucose, oxygen, lactate, and [14C]lactate as well as cerebral production of 14CO2 were measured under three conditions: 1) normoglycemia-normolactemia, 2) acute hypoglycemia-normolactemia, and 3) hypoglycemia-steady-state hyperlactemia. Although uptake of tracer [14C]lactate was consistent, there was no net uptake of unlabeled lactate during either normoglycemia or hypoglycemia. When arterial lactate concentration was raised from 2.2 +/- 0.5 to 3.3 +/- 0.4 (SE) mM by sodium lactate infusion, however, lactate was taken up. Comparison of cerebral [14C]lactate uptake with 14CO2 production indicated that the principal metabolic fate of lactate is oxidation. At increased concentrations, exogenous lactate accounted for approximately 7% of cerebral oxygen consumption. This study demonstrates that lactate crosses the blood-brain barrier of the near-term fetal sheep, is oxidized, and at elevated concentrations can partially replace glucose as an oxidative substrate during acute hypoglycemia.
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83
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Curran-Everett D, Zhang Y, Jones RH, Jones MD. Hypoxia, hypercapnia, and hypertension: their effects on pulsatile cerebral blood flow. J Appl Physiol (1985) 1995; 79:870-8. [PMID: 8567530 DOI: 10.1152/jappl.1995.79.3.870] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Pulsatile cerebral blood flow reflects characteristics of arterial blood pressure as well as the structure and mechanical properties of the cerebrovascular network. Although the effects of changes in systemic blood gases and blood pressure on mean cerebral flow are established, their effects on pulsatile cerebral blood flow are unknown. These studies assessed the effects of hypoxia-hypercapnia (combined; both arterial PO2 and PCO2 approximately 55 Torr) and acute hypertension (+30-35 mmHg by aortic occlusion) on pulsatile cerebral blood flow in ketamine-anesthetized rabbits. We characterized the relationship between pulsatile systemic blood pressure (Millar catheter) and cerebral cortical capillary blood-flow (laser-Doppler) by calculating the transfer function, a frequency-domain expression that relates amplitudes and phase angles of flow output to those of the pressure input. During hypoxia-hypercapnia, mean flow increased 17% (P < 0.001), but the amplitude and contour of pulsatile cortical blood flow were unchanged (P > 0.10). Although aortic occlusion, during hypoxia-hypercapnia as well as during normoxia-normocapnia, increased systemic pulse pressure by 40%, the amplitude of cortical flow pulsations was unaffected. Changes in dynamic properties of the cerebral vasculature (P < 0.0001 by analysis of the transfer function) minimized alterations in pulsatile cortical blood flow and thus intrabeat vessel wall stress during acute hypertension; on the basis of analysis of an electrical analogue, we propose that these changes reflect alterations in both resistance and compliance.
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84
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Hensel M, Shea JE, Gleeson C, Jones MD, Dalton E, Holden DW. Simultaneous identification of bacterial virulence genes by negative selection. Science 1995; 269:400-3. [PMID: 7618105 DOI: 10.1126/science.7618105] [Citation(s) in RCA: 995] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
An insertional mutagenesis system that uses transposons carrying unique DNA sequence tags was developed for the isolation of bacterial virulence genes. The tags from a mixed population of bacterial mutants representing the inoculum and bacteria recovered from infected hosts were detected by amplification, radiolabeling, and hybridization analysis. When applied to a murine model of typhoid fever caused by Salmonella typhimurium, mutants with attenuated virulence were revealed by use of tags that were present in the inoculum but not in bacteria recovered from infected mice. This approach resulted in the identification of new virulence genes, some of which are related to, but functionally distinct from, the inv/spa family of S. typhimurium.
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85
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Jones MD, Petrikovsky BM, Sahdev I, Prisco M. Continuous fetal heart rate monitoring during bone marrow harvesting in pregnancy. Am J Perinatol 1995; 12:243-4. [PMID: 7575825 DOI: 10.1055/s-2007-994463] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
To date, our computer-assisted search failed to report any case involving a gravid patient donating her bone marrow for harvesting. It is known that bone marrow harvesting causes a significant decrease in the donor's blood volume and therefore this can be potentially detrimental to both the mother and the fetus. We report the first case of the gravid donor in which fetal heart rate (FHR) during bone marrow harvesting has been studied. Decreased beat to beat variability and disappearance of accelerations were noted. The FHR returned to normal shortly after the procedure was terminated.
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86
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Lu HS, Hara S, Wong LW, Jones MD, Katta V, Trail G, Zou A, Brankow D, Cole S, Hu S. Post-translational processing of membrane-associated neu differentiation factor proisoforms expressed in mammalian cells. J Biol Chem 1995; 270:4775-83. [PMID: 7876250 DOI: 10.1074/jbc.270.9.4775] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Expression vectors constructed from human and rat pro-neu differentiation factor (NDF) cDNAs were transfected in Chinese hamster ovary cells for expression of recombinant NDF molecules. Soluble NDF forms were released into culture medium after post-translational processing of the membrane-bound pro-NDF forms. Different human and rat NDF isoforms, after being purified from the culture medium, were subjected to structural and biochemical characterizations. The isolated human and rat NDF isoforms have been proteolytically processed at a specific site at the N terminus, which is different from that observed for the processing of rat or human NDF molecule prepared from natural origins. The processing of each recombinant NDF isoform at its C terminus was heterogeneous but consistently occurred at nearby peptide bonds. Specific N- and C-terminal processing by Chinese hamster ovary cells has resulted in the production of two types (alpha and beta) of recombinant NDFs containing 222-225 amino acid residues. Both human and rat NDF molecules are heavily glycosylated at two of the three potential Asn-linked glycosylation sites and contain O-linked sugars at 11 of the Thr/Ser sites. Glycosylation occurs at a short, Ser/Thr-rich spacer region that connects the N-terminal immunoglobulin homology unit to the epidermal growth factor domain. Cellular phosphorylation assay indicated that these secreted forms contain similar biological activity in receptor tyrosine autophosphorylation of mammary tumor cells.
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87
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DeProspo D, Kalelkar M, Aderholz M, Akbari H, Allport PP, Ammosov VV, Andryakov A, Asratyan A, Badyal SK, Ballagh HC, Baton J, Barth M, Bingham HH, Brucker EB, Burnstein RA, Cence RJ, Chatterjee TK, Clayton EF, Corrigan G, Coutures C, Ermolov P, Erofeeva I, Faulkner PJ, Foeth H, Fretter WB, Gapienko G, Gupta VK, Hanlon J, Harigel G, Harris FA, Ivanilov A, Jabiol M, Jacques P, Jain V, Jones GT, Jones MD, Kafka T, Kaftanov V, Kasper P, Kobrin V, Kohli JM, Koller EL, Korablev V, Kubantsev M, Lauko M, Lukina O, Lys JE, Lyutov S, Marage P, Milburn RH, Mittra IS, Mobayyen MM, Moreels J, Morrison DR, Moskalev V, Murzin V, Myatt G, Nailor P, Naon R, Napier A, Neveu M, Passmore D. Neutral strange particle production in neutrino and antineutrino charged-current interactions on neon. PHYSICAL REVIEW. D, PARTICLES AND FIELDS 1994; 50:6691-6703. [PMID: 10017647 DOI: 10.1103/physrevd.50.6691] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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88
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Tinker PB, Durall DM, Jones MD. Carbon use efficiency in mycorrhizas theory and sample calculations. THE NEW PHYTOLOGIST 1994; 128:115-122. [PMID: 33874536 DOI: 10.1111/j.1469-8137.1994.tb03994.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The benefit to a fungus by a mycorrhizal association is that it gains carbon from its host. A benefit to a host is usually a nutritional one, but any resulting increase in dry weight may be counteracted by the carbon consumed by the fungus. The carbon costs of mycorrhizal fungi have been calculated using 14 C pulse-chase experiments in the laboratory or by estimating turnover rates in the field. Both of these techniques have their limitations, but estimates have been remarkably consistent amongst most laboratory studies. Carbon demands of the fungus may not reduce theoretical growth enhancement in plants which are sink-limited but would be expected to do so iii source-limited plants. A model of carbon use efficiency is developed based on the economic concepts of cost and benefit. Efficiency is defined in terms of carbon gained via the growth response to infection, and the carbon expended supporting the fungus. Practical considerations of measuring carbon allocation, and calculating carbon use efficiency are discussed. In an experiment on Salix viminalis L., colonized by Thelephora terrestris (Ehrh.) Fr., the carbon use efficiency calculated by this method was on overage 85% based on shoot tissue production, and 95% based on whole plant production.
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89
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Leite LP, Jones MD, Panasuk DB. Tracheal occlusion. Chest 1994; 105:1921-2. [PMID: 8205927 DOI: 10.1378/chest.105.6.1921a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
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90
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Webb JC, Patel DD, Jones MD, Knight BL, Soutar AK. Characterization and tissue-specific expression of the human 'very low density lipoprotein (VLDL) receptor' mRNA. Hum Mol Genet 1994; 3:531-7. [PMID: 8069294 DOI: 10.1093/hmg/3.4.531] [Citation(s) in RCA: 104] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
A cDNA has been isolated from human heart that is homologous to a member of the low density lipoprotein (LDL) receptor gene family recently identified in rabbit. It was named the very low density lipoprotein (VLDL) receptor, although its physiological function is not yet known. The predicted human protein shows 97.4% sequence homology to the rabbit protein, much more than the approximately 75% observed between their LDL receptor proteins. The sequence is also highly conserved in the hamster and the African green monkey. The mRNA was identified as a 3.9 kb transcript by Northern blotting in Hep G2 cells, cultured arterial smooth muscle cells and human skin fibroblasts, where its level was unaffected by sterols. The mRNA was not detected in EBV-lymphoblasts or in monocyte-macrophages by Northern blotting or by RT-PCR. In human tissues in vivo, the mRNA was expressed predominantly in heart and skeletal muscle, and also in ovary and kidney, but not in the liver. Although the 3.9 kb mRNA was the major transcript, a larger variant of 5.2 kb was also detectable and was predominant in skeletal muscle. Amplification of the mRNA from cultured human cells also revealed a potential splice variant that lacked 84 bp coding for a region equivalent to the O-linked sugars domain of the LDL receptor. It was a minor component in most cell types, but was predominant in Hep G2 cells.
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91
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Jones MD. Tissue oxygen transport: lessons from muscle and brain. Semin Hematol 1994; 31:102-11. [PMID: 8066466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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92
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O'Brien TP, Gleason CA, Jones MD, Cone EJ, London ED, Traystman RJ. Cerebral responses to single and multiple cocaine injections in newborn sheep. Pediatr Res 1994; 35:339-43. [PMID: 8190523 DOI: 10.1203/00006450-199403000-00013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Newborn infants exposed to cocaine near birth display a wide range of neurologic abnormalities, but the mechanism or mechanisms for these injuries remain unknown. We studied the cerebral effects of a single acute dose (4 mg/kg; n = 7) and multiple binge doses (4 mg/kg hourly for 5 h; n = 7) of i.v. cocaine in unanesthetized newborn (5 +/- 1 d old) sheep. We measured cerebral blood flow, mean arterial blood pressure, arterial blood gases, and cerebral O2 metabolism. Measurements were made at baseline; 30 s; and 5, 15, and 60 min after a single injection of cocaine in the acute group and at the same time intervals after the 5th dose of cocaine in the binge group. CBF increased by 98 +/- 68% (mean +/- SD) at 30 s after a single acute dose and by 97 +/- 94% at 30 s after the 5th of five hourly binge doses. Although it returned to baseline by 5 min in the acute group, cerebral blood flow remained elevated 5, 15, and 60 min after the 5th cocaine dose in the binge group. At 30 s, mean arterial blood pressure increased by 57 +/- 21% in the acute group and 46 +/- 15% in the binge group. In both groups, mean arterial blood pressure remained elevated at 5 min. Although no change occurred in cerebral O2 metabolism in the acute group, an increase in cerebral O2 consumption (7.4 +/- 1.3 mL/100 g/min versus 5.5 +/- 1.1 at baseline) was observed at 5 min in the binge group.(ABSTRACT TRUNCATED AT 250 WORDS)
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93
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Helou S, Koehler RC, Gleason CA, Jones MD, Traystman RJ. Cerebrovascular autoregulation during fetal development in sheep. THE AMERICAN JOURNAL OF PHYSIOLOGY 1994; 266:H1069-74. [PMID: 8160810 DOI: 10.1152/ajpheart.1994.266.3.h1069] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
There are scant data regarding the development of cerebrovascular autoregulation in fetuses. We tested the hypothesis that a decrease in cerebrovascular resistance (CVR) at reduced cerebral perfusion pressure (CPP) is absent in midgestation and near-term fetal sheep. Catheters were chronically implanted for microsphere determination of cerebral blood flow (CBF) in 9 fetuses at 92 days and in 10 fetuses at 132 days gestation (full term = 145 days). CPP was reduced by ventricular infusion of artificial cerebrospinal fluid. In 92-day fetuses, CPP was reduced stepwise from 35 to 25 and 18 mmHg and CBF decreased from 52 +/- 5 to 43 +/- 4 and 27 +/- 5 (SE) ml.min-1 x 100 g-1, respectively. Half of the immature fetuses showed some reduction in CVR at moderate reduction in CPP; however, there was no significant change in CVR in the group as a whole (from 0.72 +/- 0.06 to 0.61 +/- 0.04 and 0.89 +/- 0.20 mmHg.ml-1.min.100 g). In 132-day fetuses, CPP was reduced from 45 to 33 and 28 mmHg and CBF was unchanged (from 105 +/- 7 to 97 +/- 11 and 89 +/- 8 ml.min-1 x 100 g-1). CVR decreased from 0.45 +/- 0.05 to 0.41 +/- 0.08 and 0.33 +/- 0.03 mmHg.ml-1.min.100 g. There were no significant changes in arterial blood gases at reduced CPP in either age group. We conclude that cerebrovascular autoregulation at reduced CPP is not well developed at 92 days (0.63 gestation) in fetal sheep but that autoregulatory capacity is evident near term. We speculate that poor autoregulation may place the premature fetal brain at risk for injury.
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Walker LK, Short BL, Gleason CA, Jones MD, Traystman RJ. Cerebrovascular response to carbon dioxide in lambs receiving extracorporeal membrane oxygenation. Crit Care Med 1994; 22:291-8. [PMID: 8306689 DOI: 10.1097/00003246-199402000-00021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
OBJECTIVE To determine if the institution of extracorporeal membrane oxygenation (ECMO) alters the cerebrovascular response to changes in PaCO2. DESIGN Prospective, randomized, controlled animal trial. SUBJECTS Anesthetized 1- to 7-day-old lambs of mixed breed (n = 16). SETTING University research laboratory. INTERVENTIONS The experimental group was placed on ECMO. Both experimental and control groups (n = 8) were exposed to three concentrations of PaCO2 (hypocarbia, normocarbia, and hypercarbia) by varying mechanical ventilation and by adding carbon dioxide to the ventilator gases. MEASUREMENTS AND MAIN RESULTS Cerebral blood flow was measured by the radiolabeled microsphere method. Arterial blood gases and sagittal sinus blood gases were drawn at the time of cerebral blood flow measurement so that cerebral metabolism, cerebral oxygen transport, and extraction could be calculated. In the control group, as PaCO2 increased from 34 +/- 2 (SD) to 53 +/- 4 torr (4.5 +/- 0.3 to 7.1 +/- 0.5 kPa), cerebral blood flow increased from 53 +/- 12 to 147 +/- 50 mL/min/100 g. This increase in cerebral blood flow was not different from that of the ECMO group, where PaCO2 increased from 33 +/- 2 to 56 +/- 3 torr (4.4 +/- 0.3 to 7.5 +/- 0.4 kPa) and cerebral blood flow increased from 48 +/- 17 to 106 +/- 38 mL/min/100 g. As PaCO2 decreased from 34 +/- 2 to 19 +/- 2 torr (4.5 +/- 0.27 to 2.5 +/- 0.27 kPa), cerebral blood flow decreased from 53 +/- 12 to 43 +/- 8 mL/min/100 g in the control group. This decrease was not different from that of the ECMO group, where cerebral blood flow decreased from 48 +/- 17 to 39 +/- 10 mL/min/100 g as PaCO2 decreased from 33 +/- 2 to 22 +/- 3 torr (4.4 +/- 0.3 to 2.9 +/- 0.4 kPa). When regional cerebral blood flow was analyzed, no regional differences in the cerebrovascular responses to PaCO2 between ECMO and control groups were found. The cerebral metabolic rate was not different between ECMO and control groups at any level of PaCO2, nor was the cerebral metabolic rate affected by changes in PaCO2. Oxygen extraction increased with hypocarbia and decreased with hypercarbia in a similar fashion in both ECMO and control groups. CONCLUSION The cerebrovascular response to changes in PaCO2 was unaffected by ECMO.
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95
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Dilworth SM, Brewster CE, Jones MD, Lanfrancone L, Pelicci G, Pelicci PG. Transformation by polyoma virus middle T-antigen involves the binding and tyrosine phosphorylation of Shc. Nature 1994; 367:87-90. [PMID: 7509037 DOI: 10.1038/367087a0] [Citation(s) in RCA: 164] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Polyoma virus middle T-antigen converts normal fibroblasts to a fully transformed, tumorigenic phenotype. It achieves this, at least in part, by binding and activating one of the non-receptor tyrosine kinases, pp60c-src, pp62c-yes or pp59c-fyn (reviewed in refs 2 and 3). As a result, middle T-antigen itself is phosphorylated on tyrosine residues, one of which (Tyr 315) acts as a binding site for the SH2 domains of phosphatidylinositol-3'OH kinase 85K subunit. Here we show that another tyrosine phosphorylation site in middle T-antigen (Tyr 250; refs 4, 5) acts as a binding region for the SH2 domain of the transforming protein Shc. This results in Shc also becoming tyrosine-phosphorylated and binding to the SH2 domain of Grb2 (ref. 10). This probably stimulates p21ras activity through the mammalian homologue of the Drosophila guanine-nucleotide-exchange factor Sos (reviewed in ref. 11). We suggest that middle T-antigen transforms cells by acting as a functional homologue of an activated tyrosine kinase-associated growth-factor receptor.
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96
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Jones MD, Merewether LA, Clogston CL, Lu HS. Peptide map analysis of recombinant human granulocyte colony stimulating factor: elimination of methionine modification and nonspecific cleavages. Anal Biochem 1994; 216:135-46. [PMID: 7510935 DOI: 10.1006/abio.1994.1017] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Procedures for HPLC peptide map analysis of recombinant human granulocyte colony stimulating factor include reduction and S-carboxymethylation of the denatured protein, as well as protease digestion with Staphylococcus aureus endoproteinase Glu-C followed by reverse-phase liquid chromatographic separations. Under nonoptimized experimental conditions analytical problems including methionine modification during carboxymethylation, as well as generation of large, insoluble fragments and nonspecific cleavages during proteolytic digestion, occurred. These problems have complicated the analysis of peptide digests and affected the performance of HPLC columns. This report describes the elimination of these problems by optimizing peptide mapping procedures. We found that mild reduction and alkylation conditions can prevent methionine modification, while protease digestion in the presence of urea at room temperature alleviates generation of peptides derived from incomplete digestion and nonspecific cleavage by endoproteinase Glu-C. Peptide maps generated using the optimized procedures contain fewer peptide peaks with higher recovery. Elimination of incomplete digestion, which generates fewer larger, insoluble peptides, substantially extends the life of reverse-phase columns. The optimized method reproducibly produced peptide maps suitable for routine analysis.
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97
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Jones MD, Teo IA. Identification and analysis of the transport/capsid assembly protein (tp/cap) gene of human herpesvirus-6 (HHV6). Virology 1993; 197:449-54. [PMID: 8212582 DOI: 10.1006/viro.1993.1610] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The transport/capsid assembly protein (tp/cap) gene of human herpesvirus 6 (HHV6) strain U1102 has been identified and localized on the restriction enzyme map of the viral genome, to the EcoRI-Q fragment. The complete DNA sequence of the tp/cap gene was determined. The tp/cap gene encodes a protein product of 726 amino acids and has the strongest similarity with the homologous gene (HCMV UL56) from HCMV. Upstream of the tp/cap open reading frame is the gene for the major DNA binding protein (mdbp) and downstream is the glycoprotein B (gB) gene. This gene block arrangement is common to all herpesviruses.
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Kearney ML, Backofen JE, Koehler RC, Jones MD, Traystman RJ. Effect of hypoxemia on the cardiovascular response to intracranial hypertension in postnatal lambs. THE AMERICAN JOURNAL OF PHYSIOLOGY 1993; 265:H1557-63. [PMID: 8238567 DOI: 10.1152/ajpheart.1993.265.5.h1557] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Large increases in intracranial pressure in fetal sheep result in more potent peripheral vasoconstriction and better maintenance of cerebral O2 consumption (CMRO2) than in postnatal sheep. The fetus is exposed to a lower PO2. We tested the hypothesis that low PO2 in postnatal lambs potentiates peripheral vasoconstriction and better maintains cerebral perfusion pressure and CMRO2. Pentobarbital-anesthetized lambs, 2-7 days old, were ventilated with either room air (n = 7) or a low O2 mixture to reduce arterial O2 saturation to 50% (n = 7). Elevation of intracranial pressure to within 3-5 mmHg of baseline mean arterial pressure for 30 min by ventricular fluid infusion initially caused a similar increase in arterial pressure in the normoxic [11 +/- 3 (SE) mmHg] and hypoxic (14 +/- 2 mmHg) groups. Plasma catecholamines increased more rapidly in the hypoxic group. However, plasma vasopressin levels were substantially elevated by hypoxia alone and failed to increase further with elevated intracranial pressure. Moreover, there was no significant difference between groups in the steady-state increase in arterial pressure, and microsphere-determined blood flow to intestines, kidney, skin, and muscle did not decrease in either group. Consequently, cerebral perfusion pressure, regional cerebral blood flow, and CMRO2 were reduced similarly in both groups. Therefore, hypoxemia failed to potentiate the postnatal pressor response. Low PO2 is unlikely to be the major mechanism for the potent Cushing response in the fetus.
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Gleason CA, Iida H, O'Brien TP, Jones MD, Cone EJ, Traystman RJ. Fetal responses to acute maternal cocaine injection in sheep. THE AMERICAN JOURNAL OF PHYSIOLOGY 1993; 265:H9-14. [PMID: 8342669 DOI: 10.1152/ajpheart.1993.265.1.h9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Maternal cocaine abuse has been associated with neonatal neurological and neurobehavioral problems of unknown pathogenesis. We administered a single intravenous dose of cocaine (2 mg/kg) to 12 unanesthetized pregnant sheep; their fetuses had been catheterized in utero 2 days before the study. We measured fetal cerebral blood flow (CBF), cerebral metabolic rate of O2 (CMRO2), mean arterial blood pressure (MAP), and blood gases before and 2, 5, 15, and 30 min after maternal cocaine injection. Fetal CBF increased by 37 +/- 33% (mean +/- SD) at 5 min and returned to baseline by 15 min. Regional brain blood flow changes paralleled CBF changes with the greatest increases occurring in cerebellum (54 +/- 43%) and brain stem (54 +/- 52%). Cerebral vascular resistance was decreased for cerebellum (22%) and brain stem (19%) but was unchanged for cerebral hemispheres and caudate. Increased CBF at 5 min was associated with a 20 +/- 9% increase in fetal MAP and a 38 +/- 13% decrease in fetal arterial O2 content. Fetal CMRO2 was unchanged. There was a decrease in fetal intestinal blood flow at 2 min, an increase in myocardial, adrenal, and renal blood flow at 5 min, and no change in placental blood flow. Maternal cocaine injection causes fetal hypoxemia, hypertension, and increased CBF. Possible mechanisms for cerebral vasodilation (in some areas) include hypoxemia, impaired autoregulatory response to increased blood pressure, and/or direct or indirect vascular effects of cocaine or its metabolites.
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Smith PR, Gao Y, Karran L, Jones MD, Snudden D, Griffin BE. Complex nature of the major viral polyadenylated transcripts in Epstein-Barr virus-associated tumors. J Virol 1993; 67:3217-25. [PMID: 8098777 PMCID: PMC237661 DOI: 10.1128/jvi.67.6.3217-3225.1993] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The most abundant polyadenylated viral transcripts in the Epstein-Barr virus (EBV)-associated tumor nasopharyngeal carcinoma are a family (apparent sizes, 4.8, 5.2, 6.2, and 7.0 kb) of highly spliced cytoplasmic RNAs expressed from the BamHI-I and -A regions of the viral genome in an antisense direction with respect to several viral lytic functions encoded within the same region and concerned with the lytic cycle of the virus. We have called these complementary-strand transcripts. They are also expressed in B cells, including Burkitt's lymphoma and EBV-immortalized marmoset cell lines, and tumors generated in cottontop tamarins in response to EBV infection, but at a lower level. The complete structure of the major 4.8-kb RNAs (seven or eight exons) was determined in this study; the larger, but related, transcripts appear to be produced by differential splicing. The transcriptional promoter for the major complementary-strand transcripts, located in BamHI-I, contains several well-characterized transcriptional control elements (E2A, SP1, and AP1) and is functionally active in both B lymphocytes and epithelial cells. It appears to be a bifunctional viral promoter, as it also contains the initiation codon for a gene (BILF2) that encodes a glycoprotein that is expressed off the other strand. Splicing events create a number of small AUG-initiated open reading frames, one of which has homology to functionally significant regions of the EBV-encoded nuclear antigen 2 and to E2 (in papillomavirus). The complex nature of these transcripts and their potential role in the virus association with malignancy are considered.
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