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Sandoval Karamian AG, Yang QZ, Tam LT, Rao VL, Tong E, Yeom KW. Intracranial Hemorrhage in Term and Late-Preterm Neonates: An Institutional Perspective. AJNR Am J Neuroradiol 2022; 43:1494-1499. [PMID: 36137666 PMCID: PMC9575529 DOI: 10.3174/ajnr.a7642] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Accepted: 07/27/2022] [Indexed: 01/26/2023]
Abstract
BACKGROUND AND PURPOSE Distribution of intracranial hemorrhage in term and late-preterm neonates is relatively unexplored. This descriptive study examines the MR imaging-detectable spectrum of intracranial hemorrhage in this population and potential risk factors. MATERIALS AND METHODS Prevalence and distribution of intracranial hemorrhage in consecutive term/late-preterm neonates who underwent brain MR imaging between January 2011 to August 2018 were assessed. MRIs were analyzed to determine intracranial hemorrhage distribution (intraventricular, subarachnoid, subdural, intraparenchymal, and subpial/leptomeningeal), and chart review was performed for potential clinical risk factors. RESULTS Of 725 term/late-preterm neonates who underwent brain MR imaging, intracranial hemorrhage occurred in 63 (9%). Fifty-two (83%) had multicompartment intracranial hemorrhage. Intraventricular and subdural were the most common hemorrhage locations, found in 41 (65%) and 39 (62%) neonates, respectively. Intraparenchymal hemorrhage occurred in 33 (52%); subpial, in 19 (30%); subarachnoid, in 12 (19%); and epidural, in 2 (3%) neonates. Twenty infants (32%) were delivered via cesarean delivery, and 5 (8%), via instrumented delivery. Cortical vein thromboses were present in 34 (54%); periventricular or medullary vein thromboses, in 37 (59%); and cerebral venous sinus thrombosis, in 5 (8%). Thirty-seven (59%) had elevated markers of coagulopathy (international normalized ratio > 1.2, fibrinogen level < 234), 9 (14%) had a clinically meaningful elevation in the international normalized ratio (>1.4), and 3 (5%) had a clinically meaningful decrease in the fibrinogen level (<150). Three (5%) neonates had thrombocytopenia (platelet count < 100 × 103/μL). CONCLUSIONS While relatively infrequent, there was a wide distribution of intracranial hemorrhage in term and late-preterm infants; intraventricular and subdural hemorrhages were the most common types. We report a high prevalence of venous congestion or thromboses accompanying neonatal intracranial hemorrhage.
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Affiliation(s)
- A G Sandoval Karamian
- From the Division of Child Neurology (A.G.S.K.), University of Utah, Salt Lake City, Utah
| | - Q-Z Yang
- Division of Child Neurology (Q.-Z.Y.), University of North Carolina, Chapel Hill, North Carolina
| | - L T Tam
- Stanford University School of Medicine (L.T.T., V.L.R.), Palo Alto, California
| | - V L Rao
- Stanford University School of Medicine (L.T.T., V.L.R.), Palo Alto, California
| | - E Tong
- Department of Radiology (E.T., K.W.Y.), Lucile Packard Children's Hospital, Stanford University, Palo Alto, California
| | - K W Yeom
- Department of Radiology (E.T., K.W.Y.), Lucile Packard Children's Hospital, Stanford University, Palo Alto, California
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Nha TTN, Nam PH, Phuc NX, Nguyen VQ, Nam NH, Manh DH, Tam LT, Linh NTN, Khanh BTV, Lu LT, Nguyen LH, Phong PT. Sensitive MnFe 2O 4–Ag hybrid nanoparticles with photothermal and magnetothermal properties for hyperthermia applications. RSC Adv 2021; 11:30054-30068. [PMID: 35480279 PMCID: PMC9040900 DOI: 10.1039/d1ra03216j] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Revised: 10/12/2021] [Accepted: 08/22/2021] [Indexed: 12/14/2022] Open
Abstract
In this study, we present an experiment showing that designing multifunctional MnFe2O4–Ag nanoparticles to act as a dual hyperthermia agent is an efficient route for enhancing their heating ability. Interestingly, the specific absorption rate of the heteromeric MnFe2O4–Ag nanoparticles increased 2.7 times under simultaneous irradiation of a 100 Oe magnetic field and 0.14 W cm−2 laser compared to the action by the magnetic field alone, and more interestingly, is 30% higher than the sum of the two individual actions. The synergistic benefit of the magneto- and photo-thermal properties of the heteromeric structure can reduce the strengths of the magnetic field and laser intensities as well as their irradiation time to levels lower than those required in their hyperthermia applications individually. In vitro cytotoxicity analysis performed on HepG2 liver cancer and Hela cervical cancer cell lines showed that IC50 values were 83 ± 5.6 μg mL−1 (for HepG2) and 122.6 ± 19.8 μg mL−1 (for Hela cells) after 48 h of incubation, therefore, the nanoparticles are moderately cytotoxic and nontoxic to HepG2 and Hela cells, respectively; which offers the potential of safe therapy. In this study, we present an experiment showing that designing multifunctional MnFe2O4–Ag nanoparticles to act as a dual hyperthermia agent is an efficient route for enhancing their heating ability.![]()
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Affiliation(s)
- T. T. N. Nha
- Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam
| | - P. H. Nam
- Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam
- Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam
| | - N. X. Phuc
- Duy Tan University, 03 Quang Trung, Da Nang, Vietnam
| | - V. Q. Nguyen
- University of Science and Technology of Hanoi (USTH), Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam
| | - N. H. Nam
- Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam
| | - D. H. Manh
- Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam
| | - L. T. Tam
- Vinh University, 182 Le Duan, Vinh, Vietnam
| | - N. T. N. Linh
- Thai Nguyen University of Sciences, Tan Thanh Ward, Thai Nguyen City, Vietnam
| | - B. T. V. Khanh
- Faculty of Biology, VNU University of Science, Vietnam National University, Viet Nam
| | - L. T. Lu
- Institute for Tropical Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Viet Nam
| | - L. H. Nguyen
- Laboratory of Magnetism and Magnetic Materials, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam
- Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Vietnam
| | - P. T. Phong
- University of Management and Technology, Ho Chi Minh City, Vietnam
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Nha TTN, Nam PH, Phuc NX, Nguyen VQ, Nam NH, Manh DH, Tam LT, Linh NTN, Khanh BTV, Lu LT, Nguyen LH, Phong PT. Correction: Sensitive MnFe 2O 4–Ag hybrid nanoparticles with photothermal and magnetothermal properties for hyperthermia applications. RSC Adv 2021; 11:33372. [PMID: 35497547 PMCID: PMC9042298 DOI: 10.1039/d1ra90155a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 09/29/2021] [Indexed: 11/24/2022] Open
Abstract
Correction for ‘Sensitive MnFe2O4–Ag hybrid nanoparticles with photothermal and magnetothermal properties for hyperthermia applications’ by T. T. N. Nha et al., RSC Adv., 2021, 11, 30054–30068. DOI: 10.1039/D1RA03216J
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Affiliation(s)
- T. T. N. Nha
- Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam
| | - P. H. Nam
- Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam
- Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam
| | - N. X. Phuc
- Duy Tan University, 03 Quang Trung, Da Nang, Vietnam
| | - V. Q. Nguyen
- University of Science and Technology of Hanoi (USTH), Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam
| | - N. H. Nam
- Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam
| | - D. H. Manh
- Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam
| | - L. T. Tam
- Vinh University, 182 Le Duan, Vinh, Vietnam
| | - N. T. N. Linh
- Thai Nguyen University of Sciences, Tan Thanh Ward, Thai Nguyen City, Vietnam
| | - B. T. V. Khanh
- Faculty of Biology, VNU University of Science, Vietnam National University, Vietnam
| | - L. T. Lu
- Institute for Tropical Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam
| | - L. H. Nguyen
- Laboratory of Magnetism and Magnetic Materials, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam
- Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Vietnam
| | - P. T. Phong
- University of Management and Technology, Ho Chi Minh City, Vietnam
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Nogami R, Tam LT, Anh HTL, Quynh HTH, Thom LT, Nhat PV, Thu NTH, Hong DD, Wakisaka M. Growth promotion effect of steelmaking slag onSpirulina platensis. ACTA ACUST UNITED AC 2016. [DOI: 10.1088/1742-6596/704/1/012019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Smith DJ, Zhu H, Kolatkar PR, Tam LT, Baldwin TO, Roe BA, Broyles RH, Riggs AF. The hemoglobins of the bullfrog, Rana catesbeiana. The cDNA-derived amino acid sequences of the alpha chains of adult hemoglobins B and C: their roles in deoxygenation-induced aggregation. J Biol Chem 1993; 268:26961-71. [PMID: 8262931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The adult bullfrog (Rana catesbeiana) has two major tetrameric hemoglobins, B and C, which share a common beta chain but have different alpha chains. Components B and C associate upon deoxygenation to form a complex of the form BC2, a trimer of tetramers that depends on contacts between the alpha B and alpha C chains. Nucleotide sequences of cDNA transcripts for these chains have been determined. Transcripts were identified by analysis of the amino acid compositions of the tryptic peptides of the components and by partial amino acid sequencing. These results, together with the amino acid sequence of the beta chain (Tam, L.-T., Gray, G. P., and Riggs, A. F. (1986) J. Biol. Chem. 261, 8290-8294), permit an analysis of the structures of the alpha 2 beta 2 tetramers of hemoglobins B and C. Molecular modeling suggests possible residues at the alpha B-alpha C interfaces in the BC2 trimer and additional alpha C-alpha C contacts that would form a closed ring of six alpha chain subunits that would further stabilize the BC2 trimer. Phylogenetic analysis of the alpha B sequence suggests that it may be a "tadpole" chain, the temporal expression of which has shifted from larva to adult.
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Affiliation(s)
- D J Smith
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City 73190
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Tam LT, Manning D, Cox DJ, Riggs AF. The hemoglobins of the bullfrog, Rana catesbeiana. Deoxygenation-linked association of tetrameric components B and C to form the trimer BC2: sedimentation analysis and oxygen equilibria. J Biol Chem 1993; 268:26972-7. [PMID: 8262932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Hemolysates from the adult bullfrog, Rana catesbeiana, show an unusually high degree of cooperativity of oxygen binding with Hill coefficients greater than 4. The principal components of the tetrameric hemoglobin, B and C, do not show this high cooperativity when isolated, but it reappears when the components are mixed. Sedimentation velocity measurements show that the unusual behavior results from the mixed association of components B and C to form complexes larger than tetramers. Computer simulation of the sedimentation behavior of mixtures of deoxygenated B and C components shows that the gradient profiles can be satisfactorily described in terms of an equilibrium between the B and C tetramers and a BC2 trimer. The simplest model consistent with the results is the mixed association: B + C<-->BC and BC + C<-->BC2, with the second binding constant being higher than the first, indicating significant cooperativity. The extent of association is highest at low pH and low temperature. The dissociation of the B.C complex with low oxygen affinity to higher affinity B and C molecules during oxygenation results in greatly increased cooperativity of oxygen binding with higher Hill coefficients than possessed by either component alone in equilibria measured between 5 and 25 degrees C and between pH 6 and 8.
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Affiliation(s)
- L T Tam
- Department of Zoology, University of Texas, Austin 78712
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Smith DJ, Zhu H, Kolatkar PR, Tam LT, Baldwin TO, Roe BA, Broyles RH, Riggs AF. The hemoglobins of the bullfrog, Rana catesbeiana. The cDNA-derived amino acid sequences of the alpha chains of adult hemoglobins B and C: their roles in deoxygenation-induced aggregation. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)74204-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Tam LT, Manning D, Cox DJ, Riggs AF. The hemoglobins of the bullfrog, Rana catesbeiana. Deoxygenation-linked association of tetrameric components B and C to form the trimer BC2: sedimentation analysis and oxygen equilibria. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)74205-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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Abstract
Chronic (3-day) treatment with prazosin causes an increase in renal alpha 2-adrenergic receptor density and the relocation of renal tubular alpha 2-adrenergic receptors from extrajunctional to postjunctional sites. We investigated whether chronic prazosin treatment (2 mg/kg, i.p.) caused a functional alteration of other renal alpha 2-adrenergic receptors, using the isolated perfused rat kidney. Prazosin significantly reduced blood pressure and increased heart rate during the 3-day treatment. Renal nerve stimulation (2-8 Hz, 10 V, 1 msec) caused a frequency-dependent increase in renovascular resistance, which was potently blocked by prazosin in vitro in both control and prazosin-treated rat kidneys. The vasoconstrictor response to the alpha 2-adrenergic receptor-selective agonist BHT 933 (3-300 microM) was significantly higher in kidneys from prazosin-treated rats. Yohimbine (3-300 nM) potentiated the response to renal nerve stimulation in both treatment groups. The increase in vascular resistance following renal nerve stimulation was lower in kidneys from prazosin-treated rats, but the response to the alpha 1-adrenergic receptor agonist methoxamine (0.3-1 microM) was unchanged. Further studies revealed that renal nerve stimulation-evoked norepinephrine release from prazosin-treated rat kidneys was significantly lower than release from untreated controls. This response could be normalized to control levels by a combination of cocaine (10 microM) and yohimbine (100 nM). Thus, chronic prazosin treatment caused enhanced alpha 2-adrenergic receptor-mediated vasoconstriction and facilitated renal prejunctional inhibitory mechanisms. We conclude that with chronic alpha 1 adrenergic receptor blockade there is increased alpha 2-adrenergic receptor function in at least two and possibly three sites in the kidney; these include postjunctional tubular, prejunctional vascular, and possibly extra-junctional vascular sites.
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Skidgel RA, Schulz WW, Tam LT, Erdös EG. Human renal angiotensin I converting enzyme and neutral endopeptidase. Kidney Int Suppl 1987; 20:S45-8. [PMID: 3037174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Pettinger WA, Jeffries WB, Tam LT. Renal alpha 2-adrenoceptors as potential targets for converting enzyme inhibitors. Kidney Int Suppl 1987; 20:S191-2. [PMID: 3037170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Pettinger WA, Fallet R, Wang Y, Tam LT, Jeffries WB. Enhanced cAMP response to vasopressin in the CCT of DOCA-Na hypertensive rats. Am J Physiol 1986; 251:F1096-100. [PMID: 3024505 DOI: 10.1152/ajprenal.1986.251.6.f1096] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
We characterized altered adenosine 3',5'-cyclic monophosphate (cAMP) regulation in deoxycorticosterone acetate (DOCA)-Na hypertensive rats using endogenous cAMP accumulation in the intact cell system of microdissected renal tubule fragments. Increased cAMP accumulation in response to vasopressin (VP) in cortical collecting tubules (CCT) began on day 5 (67%) after exposure to DOCA-Na and increased by 320% on day 42. Increased blood pressure began after day 7 and polyuria after day 17. The increased response to VP was DOCA dependent and appears to be exaggerated by dietary NaCl. Anatomic and hormone specificity studies were done on days 21-30. These included cAMP responses to prostaglandin E2, parathyroid hormone, thyrocalcitonin, VP, and isoproterenol in the CCT. The cAMP response to VP was measured in the glomerulus, proximal convoluted tubule, thin descending limb of Henle, medullary thick ascending limb of Henle, cortical thick ascending limb of Henle, medullary collecting tubule, and CCT. The supersensitivity occurred only to VP and only in the CCT. Thus this alteration in the VP response is anatomic and hormone specific and does not appear to be an acute effect of DOCA, since it was not present on day 1 and on day 3 of DOCA exposure. DOCA-Na hypertension is VP dependent. A specific exaggerated cAMP response to this hormone in the CCT would be expected to cause increased sodium retention. Whether increased sodium retention at this site contributes to hypertension in the DOCA-Na rat is unknown.
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Tam LT, Gray GP, Riggs AF. The hemoglobins of the bullfrog Rana catesbeiana. The structure of the beta chain of component C and the role of the alpha chain in the formation of intermolecular disulfide bonds. J Biol Chem 1986; 261:8290-4. [PMID: 3487542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The adult bullfrog Rana catesbeiana has two major hemoglobin components, B and C. Component C polymerizes by disulfide bond formation between tetramers but component B does not. The amino acid sequence of the first 112 residues of the beta chain of component C has been reported (Baldwin, T. O., and Riggs, A. (1974) J. Biol. Chem. 249, 6110-6118). We have completed the sequence of the beta chain of component C by determining the last 28 residues. This segment contains the 2 cysteinyl residues of the chain. Examination of models indicates that neither of these is in a readily accessible position for the formation of intertetramer disulfide bonds. Reactive sulfhydryl groups of the alpha chains are shown to be responsible for the initial formation of disulfide bonds between tetramers. The beta chains within the tetramers form disulfide bonds only when the hemoglobin molecules are subjected to prolonged incubation at 37 degrees C under oxygen. The beta chains of components B and C appear to be identical; the alpha chains are clearly quite different. This suggests that the alpha B and alpha C subunits interact in the association of the deoxygenated tetramers B and C to form what appears to be a BC2 molecule.
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Tam LT, Gray GP, Riggs AF. The hemoglobins of the bullfrog Rana catesbeiana. The structure of the beta chain of component C and the role of the alpha chain in the formation of intermolecular disulfide bonds. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(19)83909-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Noble RW, Kwiatkowski LD, De Young A, Davis BJ, Haedrich RL, Tam LT, Riggs AF. Functional properties of hemoglobins from deep-sea fish: correlations with depth distribution and presence of a swimbladder. Biochim Biophys Acta 1986; 870:552-63. [PMID: 3697364 DOI: 10.1016/0167-4838(86)90265-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The ligand binding properties of the hemoglobins of several deep-sea, bottom-living fish have been examined. These include five species of rattails (Macrouridae) and Antimora rostrata, all of which possess swimbladders, and two unrelated species without swimbladders, Bathysaurus mollis and Alepocephalus sp. All of the hemolysates of these fish exhibited the Root effect with a minimum ligand affinity at about pH 6 in the presence of organic phosphate. Under these conditions the hemolysates from fish which possess swimbladders exhibit two roughly equal populations of heme groups with markedly different ligand affinities. For the deeper-dwelling species the affinities for carbon monoxide differ by some 500-fold, the low-affinity population having a p50(CO) of 100 mmHg at 15 degrees C. This very low affinity is associated with a second-order rate constant for CO combination of the order of 10(3) M-1 X s-1. Those species without swimbladders have hemoglobins which do not have such heterogeneous binding sites, suggesting a relationship between these very-low-affinity heme groups and the pumping of oxygen into a swimbladder at high hydrostatic pressures.
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Tam LT, Engelbrecht S, Talent JM, Gracy RW, Erdös EG. The importance of disulfide bridges in human endopeptidase (enkephalinase) after proteolytic cleavage. Biochem Biophys Res Commun 1985; 133:1187-92. [PMID: 3910045 DOI: 10.1016/0006-291x(85)91262-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The neutral endopeptidase (NEP) is a membrane-bound enzyme, which is solubilized by treatment with the protease, papain. Papain did not affect the apparent catalytic activity or the molecular mass of the purified human enzyme in SDS-PAGE. When NEP was treated with a reducing agent after papain digestion, it dissociated into smaller, lower molecular mass fragments. Amino acid analysis and s-carboxymethylation of the half cystine residues indicated that NEP contains four S-S bridges. We concluded that, although covalent bonds appear to be cleaved in NEP by papain, its activity and structure are sustained by S-S bridges.
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Tam LT, Riggs AF. Oxygen binding and aggregation of bullfrog hemoglobin. J Biol Chem 1984; 259:2610-6. [PMID: 6607921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The hemoglobin of the bullfrog, Rana catesbeiana, forms aggregates larger than tetramers in two ways. The first, which results from intermolecular disulfide bonds, can be prevented by treatment with iodoacetamide. The second way results from the association of the deoxygenated forms of the two major components, B and C, to form reversibly an aggregate which is believed to be a trimer, BC2. The sedimentation velocity data show that the stoichiometry of the aggregate cannot be 1:1. The electrophoretic pattern of the deoxygenated B/C mixture suggests that the association is not indefinite. No significant aggregation of the separate deoxygenated tetramers of the components nor of the oxygenated components or mixture occurs. Gel chromatography of the oxygenated forms of components B and C and of mixtures indicates that the B and C tetramers both form dimers upon dilution with a dissociation constant of 2-3 micron. The oxygen-binding data indicate that the B/C aggregate has a much lower oxygen affinity than its constituent tetramers. Dissociation of the low affinity B/C aggregate to higher affinity B and C tetramers with increasing oxygenation gives rise to enhanced cooperativity as measured by the Hill coefficient which is maximal near 75-80% oxygenation and is as high as 4.1 at a heme concentration of 15 mM.
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