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1.
Crit Care ; 27(1): 417, 2023 10 31.
Artigo em Inglês | MEDLINE | ID: mdl-37907989

RESUMO

BACKGROUND: Sepsis is one of the leading causes of death. Treatment attempts targeting the immune response regularly fail in clinical trials. As HCMV latency can modulate the immune response and changes the immune cell composition, we hypothesized that HCMV serostatus affects mortality in sepsis patients. METHODS: We determined the HCMV serostatus (i.e., latency) of 410 prospectively enrolled patients of the multicenter SepsisDataNet.NRW study. Patients were recruited according to the SEPSIS-3 criteria and clinical data were recorded in an observational approach. We quantified 13 cytokines at Days 1, 4, and 8 after enrollment. Proteomics data were analyzed from the plasma samples of 171 patients. RESULTS: The 30-day mortality was higher in HCMV-seropositive patients than in seronegative sepsis patients (38% vs. 25%, respectively; p = 0.008; HR, 1.656; 95% CI 1.135-2.417). This effect was observed independent of age (p = 0.010; HR, 1.673; 95% CI 1.131-2.477). The predictive value on the outcome of the increased concentrations of IL-6 was present only in the seropositive cohort (30-day mortality, 63% vs. 24%; HR 3.250; 95% CI 2.075-5.090; p < 0.001) with no significant differences in serum concentrations of IL-6 between the two groups. Procalcitonin and IL-10 exhibited the same behavior and were predictive of the outcome only in HCMV-seropositive patients. CONCLUSION: We suggest that the predictive value of inflammation-associated biomarkers should be re-evaluated with regard to the HCMV serostatus. Targeting HCMV latency might open a new approach to selecting suitable patients for individualized treatment in sepsis.


Assuntos
Infecções por Citomegalovirus , Sepse , Humanos , Citomegalovirus , Infecções por Citomegalovirus/complicações , Imunidade , Interleucina-6 , Sepse/complicações
2.
Radiography (Lond) ; 29(3): 610-616, 2023 05.
Artigo em Inglês | MEDLINE | ID: mdl-37086589

RESUMO

INTRODUCTION: Radiographers play a central role in patient safety because of their knowledge of and responsibilities in relation to the imaging process. To maintain safe care, the workplace must create a safety culture that enables sustainable safety work. AIM: This study aims to describe radiographers' perceptions of the patient safety culture in radiology units in Sweden. METHODS: The Swedish Hospital Survey of Patients' Safety Culture (S-HSOPSC) was used to gather descriptive data from 171 Swedish registered radiographers working in five radiology clinics distributed across 15 units. Fifty-one questionnaire items and one open-ended question were analysed, comprising perceptions of the overall safety grade, the frequency of number of reported risks and events, and 14 composites regarding patient safety dimensions. RESULTS: The radiographers' concerns surrounding the patient safety culture in their workplaces related to weaknesses regarding the safety dimensions "Staffing", "Frequency of error reporting", "Organizational learning - continuous improvement" and "Executive management support for patient safety". They perceived "Teamwork within the unit" to be a strength. CONCLUSION: Despite some weaknesses in the patient safety culture, the radiographers perceived that the overall patient safety level was good, in part because of their ability to spot risks in time. The executive management, however, needed to improve their feedback on safety measures; and another reason for some weaknesses in the patient safety culture could be staffing issues such as lack of time for meetings for continuous improvement. Managers and leaders have a great responsibility to establish a patient safety culture through support and good leadership. IMPLICATIONS FOR PRACTICE: An understanding of what creates a safety culture is important to prevent patient safety incidents.


Assuntos
Segurança do Paciente , Radiologia , Humanos , Gestão da Segurança , Radiografia , Percepção
3.
Phys Rev Lett ; 128(11): 112503, 2022 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-35363014

RESUMO

We have measured the 3d→2p transition x rays of kaonic ^{3}He and ^{4}He atoms using superconducting transition-edge-sensor microcalorimeters with an energy resolution better than 6 eV (FWHM). We determined the energies to be 6224.5±0.4(stat)±0.2(syst) eV and 6463.7±0.3(stat)±0.1(syst) eV, and widths to be 2.5±1.0(stat)±0.4(syst) eV and 1.0±0.6(stat)±0.3(stat) eV, for kaonic ^{3}He and ^{4}He, respectively. These values are nearly 10 times more precise than in previous measurements. Our results exclude the large strong-interaction shifts and widths that are suggested by a coupled-channel approach and agree with calculations based on optical-potential models.

4.
Radiography (Lond) ; 27(4): 1058-1063, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34023227

RESUMO

INTRODUCTION: Guidelines concerning intravenous iodinated contrast media (CM) during computed tomography (CT) examinations are important to follow to minimize the risk for post-contrast acute kidney injury (PC-AKI). The purpose of this study was to investigate the radiology departmental policy compliance with Swedish guidelines concerning PC-AKI. METHODS: In February 2020, an electronic survey was distributed to the responsible radiographer at 41 radiology departments in all university hospitals and medium-sized hospitals in Sweden. The questions focused on routines around renal functional tests, individualized contrast administration and handling of patients with diabetes mellitus taking metformin. RESULTS: The response rate was 83%. Seventy-six percent (n = 26) of radiology departments calculated estimated glomerular filtration rate (eGFR) from serum creatinine prior to CM administration, but only 24% (n = 8) followed the recommendation to calculate eGFR from both serum creatinine and cystatin C. For acute/inpatients, 55% (n = 18) followed the recommendation that renal functional tests should be performed within 12 h before CM administration. For elective patients, 97% (n = 33) followed the recommendation to have eGFR newer than three months which is acceptable for patients with no history of disease that may have affected renal function. Approximately 80% of the radiology departments followed the recommendation that CM dose always should be individually adjusted to patient eGFR. Seventy-six percent (n = 26) followed the recommendation to continue with metformin at eGFR ≥ 45 ml/min. CONCLUSION: Compliance with the national guidelines was high regarding routines around renal functional tests, dose adjustment of CM and metformin discontinuation. Improvements can be made in using both cystatin C and serum creatinine for eGFR calculations as well as ensuring renal function tests within 12 h for acute/inpatients with acute disease that may affect renal function. IMPLICATIONS FOR PRACTICE: This study raises awareness of the importance of adhering to guidelines in healthcare. To have knowledge about the current level of compliance regarding PCI-AKI is important to maintain and develop effective clinical implementation of guidelines. The variation in practice seen in this study emphasizes the need of more effective implementation strategies to ensure adherence with best practice.


Assuntos
Injúria Renal Aguda , Intervenção Coronária Percutânea , Radiologia , Injúria Renal Aguda/induzido quimicamente , Meios de Contraste/efeitos adversos , Fidelidade a Diretrizes , Humanos , Fatores de Risco , Suécia
5.
Eur Phys J C Part Fields ; 78(4): 319, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29706795

RESUMO

The VIolation of Pauli exclusion principle -2 experiment, or VIP-2 experiment, at the Laboratori Nazionali del Gran Sasso searches for X-rays from copper atomic transitions that are prohibited by the Pauli exclusion principle. Candidate direct violation events come from the transition of a 2p electron to the ground state that is already occupied by two electrons. From the first data taking campaign in 2016 of VIP-2 experiment, we determined a best upper limit of [Formula: see text] for the probability that such a violation exists. Significant improvement in the control of the experimental systematics was also achieved, although not explicitly reflected in the improved upper limit. By introducing a simultaneous spectral fit of the signal and background data in the analysis, we succeeded in taking into account systematic errors that could not be evaluated previously in this type of measurements.

6.
Genet Mol Res ; 13(4): 10194-203, 2014 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-25501231

RESUMO

Recent genome wide association studies identified many loci in several genes that have been consistently associated with type 2 diabetes mellitus in various ethnic populations. Among the genes that were most strongly associated with diabetes were fat mass- and obesity-associated, melanocortin 4 receptor, solute carrier family 30 member 8 (SLC30A8), and a member of the potassium voltage-gated channels. In the present study, we examined the association between variants in fat mass- and obesity-associated [rs9939609 (A/T)], melanocortin 4 receptor [rs17782313 (C/T), and rs12970134 (A/G)], SLC30A8 [rs13266634 (C/T)], and a member of the potassium voltage-gated channels [rs2237892(C/T)] genes in diabetes patients from Saudi Arabia. Genotypes were determined using the TaqMan single-nucleotide polymorphism genotype analysis technique. Minor allele frequency of the 4 variants tested was comparable between type 2 diabetes cases and controls. We observed an association between allele variants of SLC30A8 [rs13266634 (C/T)] and type 2-diabetes (P = 0.04). The other single-nucleotide polymorphisms examined in this study showed moderate or no correlation with diabetes in Saudis. Our data indicate that the SLC30A8 polymorphisms are associated with type 2 diabetes in the Saudi population. There is no evidence supporting an association between variants in the fat mass- and obesity-associated and melanocortin 4 receptor, and a member of the potassium voltage-gated channels genes and type 2 diabetes in the Saudi population.


Assuntos
Proteínas de Transporte de Cátions/genética , Diabetes Mellitus Tipo 2/genética , Canal de Potássio KCNQ1/genética , Polimorfismo de Nucleotídeo Único , Proteínas/genética , Receptor Tipo 4 de Melanocortina/genética , Adulto , Dioxigenase FTO Dependente de alfa-Cetoglutarato , Estudos de Casos e Controles , Feminino , Estudos de Associação Genética , Predisposição Genética para Doença , Genótipo , Humanos , Masculino , Pessoa de Meia-Idade , Arábia Saudita , Transportador 8 de Zinco
7.
Nucl Phys A ; 914(100): 305-309, 2013 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-24068854

RESUMO

The kaonic 3He and 4He [Formula: see text] transitions in gaseous targets were observed by the SIDDHARTA experiment. The X-ray energies of these transitions were measured with large-area silicon-drift detectors using the timing information of the [Formula: see text] pairs produced by the DAΦNE [Formula: see text] collider. The strong-interaction shifts and widths both of the kaonic 3He and 4He 2p states were determined, which are much smaller than the results obtained by the previous experiments. The "kaonic helium puzzle" (a discrepancy between theory and experiment) was now resolved.

8.
Nucl Phys A ; 907(100): 69-77, 2013 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-23805024

RESUMO

The study of the [Formula: see text] system at very low energies plays a key role for the understanding of the strong interaction between hadrons in the strangeness sector. At the DAΦNE electron-positron collider of Laboratori Nazionali di Frascati we studied kaonic atoms with [Formula: see text] and [Formula: see text], taking advantage of the low-energy charged kaons from Φ-mesons decaying nearly at rest. The SIDDHARTA experiment used X-ray spectroscopy of the kaonic atoms to determine the transition yields and the strong interaction induced shift and width of the lowest experimentally accessible level (1s for H and D and 2p for He). Shift and width are connected to the real and imaginary part of the scattering length. To disentangle the isospin dependent scattering lengths of the antikaon-nucleon interaction, measurements of [Formula: see text] and of [Formula: see text] are needed. We report here on an exploratory deuterium measurement, from which a limit for the yield of the K-series transitions was derived: [Formula: see text] and [Formula: see text] (CL 90%). Also, the upcoming SIDDHARTA-2 kaonic deuterium experiment is introduced.

9.
Phys Lett B ; 714(1): 40-43, 2012 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-22876000

RESUMO

The kaonic (3)He and (4)He X-rays emitted in the [Formula: see text] transitions were measured in the SIDDHARTA experiment. The widths of the kaonic (3)He and (4)He 2p states were determined to be [Formula: see text], and [Formula: see text], respectively. Both results are consistent with the theoretical predictions. The width of kaonic (4)He is much smaller than the value of [Formula: see text] determined by the experiments performed in the 70's and 80's, while the width of kaonic (3)He was determined for the first time.

10.
Phys Lett B ; 697(3-2): 199-202, 2011 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-21633519

RESUMO

The first observation of the kaonic (3)He 3d→2p transition was made, using slow K- mesons stopped in a gaseous (3)He target. The kaonic atom X-rays were detected with large-area silicon drift detectors using the timing information of the K+K- pairs of ϕ-meson decays produced by the DAΦNE e+e- collider. The strong interaction shift of the kaonic (3)He 2p state was determined to be -2±2(stat)±4(syst) eV.

11.
Artigo em Inglês | MEDLINE | ID: mdl-22312940

RESUMO

BACKGROUND: Asthma is a multifactorial disorder, and both genetic and environmental factors contribute to its development. We investigated the possible association between asthma and 5 single-nucleotide polymorphisms (SNPs) in the interleukin 17 (IL17) gene--rs17880588 (G/A) and rs17878530 (C/T) in IL17A and rs763780 (T/C), rs11465553 (T/C), and rs2397084 (G/A) in IL17F--and compared levels of the proteins IL17A and IL17F in asthma patients with those of controls. PATIENTS AND METHODS: The study group included 100 asthma patients and 102 ethnically matched controls. Genotyping was performed on purified DNA using reverse transcriptase-polymerase chain reaction with specific primers and probes. Levels of IL17A and IL17F were measured in plasma using enzyme-linked immunosorbent assay. RESULTS: Genotyping showed that AG heterozygotes of rs17880588 in IL17A were significantly more common in the control group than among the asthma patients (P < .05); no significant associations were observed for any of the other SNPs examined. Levels of IL17A and IL17F were both higher in asthma patients (IL17A, 2.242 [0.099] vs 2.752 [0.287] pg/mL; IL17F, 236.01 [38.28] vs 700 [201.078] pg/mL). The difference was statistically significant for IL17F (P = .025, t test). Levels of IL17A and IL17F were positively and significantly correlated in the asthma patients CONCLUSION: Of all the SNPs analyzed, only rs17880588 showed a significant association with asthma in the Saudi population we studied. Levels of IL17A and IL17F were significantly upregulated in the asthma patients. The morphology of IL17F appeared to affect expression levels.


Assuntos
Asma/genética , Interleucina-17/genética , Polimorfismo de Nucleotídeo Único , Asma/imunologia , Ensaio de Imunoadsorção Enzimática , Genótipo , Humanos , Interleucina-17/sangue
12.
Arch Biochem Biophys ; 395(2): 185-90, 2001 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-11697855

RESUMO

Interaction of camel lens zeta-crystallin, an NADPH:quinone oxidoreductase, with several quinone derivatives was examined by fluorescence spectroscopy and activity measurements. Fluorescence of zeta-crystallin was quenched to different levels by the different quinones:juglone (5-OH, 1,4 naphthoquinone), 1,4 naphthoquinone (1,4-NQ), and 1,2 naphthoquinone (1,2-NQ) considerably quenched the fluorescence of zeta-crystallin, where as the commonly used substrate, 9,10-phenanthrenequinone (PQ) did not induce significant quenching. Activity measurements showed only PQ served as a substrate for camel lens zeta-crystallin, while juglone, 1,4-NQ, and 1,2-NQ were inhibitors. Thus quinones that interacted with zeta-crystallin directly inhibited the enzyme, whereas the substrate had very low affinity for the enzyme in the absence of NADPH. Another substrate, dichlorophenol indophenol (DCIP), conformed to the same pattern; DCIP did not quench the fluorescence of the enzyme significantly, but served as a substrate. This pattern is consistent with an ordered mechanism of catalysis with quinone being the second substrate. All three naphthoquinones were uncompetitive inhibitors with respect to NADPH and noncompetitive with respect to PQ. These kinetics are similar to those exhibited by cysteine- and/or lysine-modifying agents. Juglone, 1,4-NQ, and 1,2-NQ interacted with and quenched the fluorescence of camel lens alpha-crystallin, but to lesser extent than that of zeta-crystallin.


Assuntos
Cristalinas/química , Cristalinas/metabolismo , Cristalino/química , 2,6-Dicloroindofenol/farmacologia , Animais , Camelus , Catálise , Cisteína/química , Relação Dose-Resposta a Droga , Cinética , Ligantes , NADP/metabolismo , Naftoquinonas/farmacologia , Ligação Proteica , Espectrometria de Fluorescência
13.
Biochim Biophys Acta ; 1544(1-2): 283-8, 2001 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-11341937

RESUMO

Fluorescence spectrum of camel lens zeta-crystallin, a major protein in the lens of camelids and histicomorph rodents, showed maximum emission at 315 nm. This emission maximum is blue shifted compared to most proteins, including alpha-crystallin, and appeared to be due to tryptophan in highly hydrophobic environment. Interaction of NADPH with zeta-crystallin quenched the protein fluorescence and enhanced the fluorescence of bound NADPH. Analysis of fluorescence quenching suggested high-affinity interaction between NADPH and zeta-crystallin with an apparent Km<0.45 microM. This value is at least an order of magnitude lower than that suggested by activity measurements. Analysis of NADPH fluorescence showed a biphasic curve representing fluorescence of free- and bound-NADPH. The intersection between free- and bound-NADPH closely paralleled the enzyme concentration, suggesting one mole of NADPH was bound per subunit of the enzyme. Phenanthrenequinone (PQ), the substrate of zeta-crystallin, also was able to quench the fluorescence of zeta-crystallin, albeit weaker than NADPH. Quantitative analysis suggested that zeta-crystallin had low affinity for PQ in the absence of NADPH, and PQ binding induced significant conformational changes in zeta-crystallin.


Assuntos
Cristalinas/metabolismo , NADP/metabolismo , Animais , Camelus , Ligação Proteica , Espectrometria de Fluorescência
14.
Biochim Biophys Acta ; 1546(1): 71-8, 2001 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-11257509

RESUMO

Interaction of camel lens zeta-crystallin with the hydrophobic probe 1-anilinonaphthalene-8-sulfonic acid (ANS) enhanced the ANS fluorescence and quenched the protein fluorescence. Both of these events were concentration-dependent and showed typical saturation curves suggesting specific ANS-zeta-crystallin binding. Quantitative analysis indicated that 1 mole zeta-crystallin bound at most 1 mole ANS. NADPH but not 9,10-phenanthrenequinone (PQ) was able to displace zeta-crystallin-bound ANS. These results suggested the presence of a hydrophobic domain in zeta-crystallin, possibly at the NADPH binding site. alpha-Crystallin as well as NADPH protected zeta-crystallin against thermal inactivation suggesting the importance of this site for enzyme stability. The NADPH:quinone oxidoreductase activity of zeta-crystallin was inhibited by ANS with NADPH as electron donor and PQ as electron acceptor. Lineweaver-Burk plots indicated mixed-type inhibition with respect to NADPH, with a K(i) of 2.3 microM. Secondary plots of inhibition with respect to NADPH indicated a dissociation constant (K'I) of 12 microM for the zeta-crystallin-NADPH-ANS complex. The K(i) being smaller than K'I suggested that competitive inhibition at the NADPH binding site was predominant over non-competitive inhibition. Like ANS-zeta-crystallin binding, inhibition was dependent on ANS concentration but independent of incubation time.


Assuntos
Cristalinas/química , Cristalino/química , NADP/química , Naftalenossulfonato de Anilina/farmacologia , Animais , Ligação Competitiva , Camelus , Cristalinas/antagonistas & inibidores , Cristalinas/isolamento & purificação , Fluorescência , NAD(P)H Desidrogenase (Quinona)/antagonistas & inibidores , Propriedades de Superfície , zeta-Cristalinas
15.
Biochemistry ; 34(34): 10777-85, 1995 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-7662658

RESUMO

Annexins VI and V are members of the annexin family of proteins that bind to phospholipid membranes in a calcium-dependent manner. The dynamics of protein, calcium, and phospholipid assembly and dissociation were investigated by stopped-flow. At relatively low calcium levels, the kinetics of the binding reaction were sensitive to calcium concentration. However, in the presence of saturating levels of calcium and at relatively low protein/vesicle (w/w) ratios (0.4 or lower), the binding reactions were rapid and the rate constants were comparable to the collisional limit, about 1.4 x 10(10) M-1 s-1 for large unilamellar vesicles (about 120 nm diameter) and about 2.7 x 10(9) M-1 s-1 for small unilamellar vesicles (about 31 nm in diameter). These constants are expressed on the basis of vesicle concentration. These limiting association rate constants were not sensitive to the phospholipid composition of the vesicles. In contrast, at these calcium levels, protein dissociation was so slow that the complexes could be regarded as stable. However, individual calcium ions that were bound to the complexes appeared to exchange rapidly with ions in bulk solution. EGTA-induced protein dissociation was rapid with first-order rate constants ranging from 10 to 50 s-1. These were dependent on the membrane composition and on the protein type (annexin VI or V). Variations in this dissociation process were found to complement the calcium concentration needed to support annexin-membrane association; increasing the acidic phospholipid component or partially replacing phosphatidylcholine by phosphatidylethanolamine in the membrane decreased both the EGTA-induced dissociation rate and the calcium concentration needed to support binding.(ABSTRACT TRUNCATED AT 250 WORDS)


Assuntos
Anexina A6/metabolismo , Cálcio/metabolismo , Fosfolipídeos/metabolismo , Animais , Encéfalo/metabolismo , Cálcio/farmacologia , Bovinos , Ácido Egtázico/farmacologia , Fluorescência , Cinética , Luz , Lipossomos/química , Lipossomos/metabolismo , Tamanho da Partícula , Fosfatidilcolinas/análise , Fosfatidiletanolaminas/análise , Fosfolipídeos/química , Ligação Proteica , Espalhamento de Radiação
17.
Cell Signal ; 5(4): 357-65, 1993 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-8373720

RESUMO

Protein kinase C and the annexins appear to share some unusual and potentially important membrane- and calcium-binding properties. While these proteins are calcium response elements, they are not calcium-binding proteins in the formal sense; at intracellular calcium concentrations, they only bind significant amounts of calcium when membranes or other suitable surfaces are present. The number of calcium ions bound per protein is large (> 8) and this stoichiometry, at the protein-membrane interface, may provide the large number of contact points needed for the very high-affinity interaction that is observed. The further ability of annexins and PKC to form structures with properties of integral membrane proteins may be important to provide a type of long-term cell signalling that produces a constitutively active kinase or ion channel activity. Selectivity for phospholipids in bilayer form is modest with respect to the acidic phospholipids but there is a surprising preference for phosphatidylethanolamine as the neutral phospholipid matrix. Along with other unusual properties, these proteins offer the potential for unique types of cell regulation events.


Assuntos
Anexinas/metabolismo , Cálcio/metabolismo , Proteína Quinase C/metabolismo , Transdução de Sinais , Animais , Membrana Celular/metabolismo , Humanos , Cinética
19.
Thyroid ; 3(4): 269-72, 1993.
Artigo em Inglês | MEDLINE | ID: mdl-8118222

RESUMO

The effect of radioiodine therapy in Graves' disease is gradual in onset and the subjects continue to be hyperthyroid for several weeks after such therapy. In a prospective study of 112 patients, we compared the usefulness of two commonly employed antithyroid drug regimens in controlling hyperthyroidism in the period immediately following radioiodine therapy. They received propylthiouracil (PTU, 100 mg orally three times a day), saturated solution of potassium iodide (10 drops once a day) or no drugs starting 5 days after radioiodine therapy. Thyroid status was monitored clinically and by serum thyroxine index and TSH measured at 4-6 week intervals over a 6-month period. The control or drug-treated groups did not differ in thyroid status 6 weeks after radioiodine. The PTU-treated group had greater incidence of hyperthyroidism and a lower incidence of hypothyroidism at 6 months. However, the differences were explained on the basis of a greater incidence of large goiters that appeared to confer relative radioresistance in the PTU group. We conclude that patients with mild to moderate hyperthyroidism do not benefit from adjunctive treatment with PTU or potassium iodide immediately after radioiodine therapy.


Assuntos
Doença de Graves/radioterapia , Radioisótopos do Iodo/uso terapêutico , Iodeto de Potássio/uso terapêutico , Propiltiouracila/uso terapêutico , Adulto , Idoso , Idoso de 80 Anos ou mais , Terapia Combinada , Feminino , Doença de Graves/sangue , Doença de Graves/tratamento farmacológico , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Tireotropina/sangue , Tiroxina/sangue
20.
J Biol Chem ; 267(32): 22891-6, 1992 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-1429637

RESUMO

The activation of protein kinase C (PKC) usually displays cofactor requirements that include phosphatidylserine (PS), diacylglycerol, and calcium. A complicating factor is that good exogenous substrates of PKC are polycationic proteins or peptides that form aggregates with PS in the assay. This study examined the autophosphorylation of PKC using assays with phospholipid provided in the form of vesicles or phospholipid-Triton mixed micelles. The results showed a close correlation between PKC autophosphorylation and the formation of aggregated assay components. Aggregation occurred primarily by the action of Mg2+ on phospholipids and appeared to underlie a number of major features of PKC autophosphorylation. For example, autophosphorylation required higher concentrations of PS than phosphorylation of exogenous substrates. This appeared to be the result of the different PS requirements of aggregation by divalent metal ions and cationic substrates. An unanticipated result was that aggregation of mixed micelles showed specificity for PS, high cooperativity with respect to several agents, and a requirement for calcium. These parameters were remarkably similar to those describing PKC autophosphorylation. Several major implications are evident in this study. Since the autophosphorylation assay is not a well defined system of monodisperse materials, autophosphorylation of PKC may proceed by intra- or interpeptide mechanism. The uniform correlation between aggregation and production of PKC activity suggested that kinetic parameters may represent interactions of assay components other than the enzyme. Aggregation, which appeared necessary for in vitro activation of PKC, may represent the expression of important but undefined in vivo requirements for this enzyme's function.


Assuntos
Isoenzimas/metabolismo , Fosfolipídeos/farmacologia , Proteína Quinase C/metabolismo , Animais , Encéfalo/enzimologia , Bovinos , Cinética , Magnésio/farmacologia , Micelas , Fosforilação , Ligação Proteica , Relação Estrutura-Atividade
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