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1.
Indian J Plast Surg ; 57(4): 263-269, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-39345675

RESUMO

Background The normal ability to distinguish two points from one is known as the two-point discriminative (2PD) sense. This forms an extremely important assessment in patient with injuries to the nerves distributed to the upper extremity. Objective The aim of this study was to estimate the normal reference values of static 2PD in healthy adults and children. Materials and Methods A total of 624 normal adults comprising 380 men and 244 women were recruited randomly for the study at three different centers. Additionally, 172 healthy children, comprising 110 boys and 62 girls, were studied. Eight sensory areas in the palmar surface of the hand were delineated. The ability to distinguish the static 2PD was estimated in millimeters by using disk discriminator. The results were tabulated and statistically analyzed. Results The mean static 2PD in the adult population ranged from 2.78 to 3.5 mm in the fingertips and 5.39 to 7.13 mm in the mid-palm. There was a statistically significant difference between men and women in zones 6, 7, and 8. In children, the observed 2PD values were 2.15 to 3.63 mm in the fingertips and 4.10 to 5.77 mm in the palm. Children have a significantly better 2PD sense when compared with adults. Conclusion The normal value of static 2PD in the palmar surface of the hand among the Indian pediatric and adult populations was established in the study.

2.
Indian J Surg Oncol ; 13(3): 481-487, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-36187512

RESUMO

D2 gastrectomy is the globally accepted standard surgical procedure for operable gastric cancer, and lymph node (LN) dissection is considered as the critical part of radical surgery and closely related to the prognosis. The splenic hilar LN (SHLN) or level 10 are to be removed during standard D2 total gastrectomy. In situ and ex situ spleen-preserving lymphadenectomies have been the most common dissection approaches for SHLNs. No study exists which compares the outcomes of these techniques in Indian population. This study is aimed to analyse the operative outcomes of ex situ in vivo technique of spleen-preserving splenic hilar lymph node dissection in patients who underwent D2 total gastrectomy for operable proximal gastric cancer in comparison with in situ in vivo technique of splenic hilar lymph node dissection. We reviewed prospectively collected data from 17 patients with operable proximal gastric cancer between September 2016 and April 2019 who underwent D2 total gastrectomy with splenic hilar lymph node dissection and studied the preoperative demographic factors, operative and postoperative outcomes comparing the different operative techniques. Patients with oesophago-gastric junction involvement, direct splenic or other adjacent organ invasion requiring multivisceral resection and gastric stump carcinoma were excluded. Overall, 17 patients underwent D2 total gastrectomy for operable gastric cancer. Mean age of presentation was 54.7 years including 13 males and 4 females. Five patients had middle third and 12 patients had upper third cancer. All patients had splenic hilar nodal clearance as follows: in situ - 14 and ex situ - 3 patients. R0 resection was achieved in all patients. Lymph node harvest tends to be higher with lower operative time and blood loss in patients with ex situ technique compared to in situ technique with similar morbidity. Ex situ in vivo technique of spleen-preserving splenic hilar lymph node dissection can be considered as both safe and feasible procedure for operable proximal gastric cancer patients in experienced centres to achieve better lymph node yield with no significant increase in morbidity.

4.
J Med Case Rep ; 13(1): 160, 2019 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-31122272

RESUMO

INTRODUCTION: Duplication cyst of the alimentary tract is a rare congenital anomaly. Duodenal duplication cyst accounts for less than 5% overall. These entities rarely present in adults. They are often mistaken as choledochoceles. Management is most often complete excision, but it is individualized to the particular case. CASE PRESENTATION: A 22-year-old woman was admitted to our hospital with a history of intermittent colicky right hypochondrial pain not relieved by any medications for the past 3 months. Initially, she was given proton pump inhibitors, but her pain was not relieved. Further evaluation was done, and preoperative imaging showed a cyst in the second part of the duodenum. Magnetic resonance imaging revealed it as a choledochocele, but duodenal duplication cyst was kept in the differential diagnosis. Further ultrasound identified it to be a duplication cyst. After failed endotreatment, the patient was successfully managed with partial excision and marsupialization. CONCLUSION: Duodenal duplication cyst is uncommon and rarely diagnosed in adults. Duplications in the duodenum should always be a part of the differential diagnosis, especially in cystic lesions. Ultrasonogram of the cyst might lead to the proper diagnosis. Surgery is the treatment of choice if endotherapy is not successful.


Assuntos
Cisto do Colédoco/diagnóstico , Cisto do Colédoco/cirurgia , Anormalidades do Sistema Digestório/diagnóstico , Anormalidades do Sistema Digestório/cirurgia , Duodenopatias/diagnóstico , Duodenopatias/cirurgia , Adulto , Diagnóstico Diferencial , Feminino , Humanos , Resultado do Tratamento , Adulto Jovem
5.
Ann R Coll Surg Engl ; 99(8): e219-e220, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-29046082

RESUMO

Extra-renal calyces are a rare anomaly of the renal collecting system, characterised by the presence of calyces and pelvis outside the renal parenchyma. It may also be associated with other anomalies, such as renal ectopia, fusion and malrotation. We describe an unusual case of extra-renal calyces with six long calyces arising from a suspected multicystic dysplastic kidney that was successfully managed laparoscopically.


Assuntos
Hidronefrose , Rim , Laparoscopia/métodos , Nefrectomia/métodos , Feminino , Humanos , Hidronefrose/diagnóstico por imagem , Hidronefrose/patologia , Hidronefrose/cirurgia , Lactente , Rim/anormalidades , Rim/diagnóstico por imagem , Rim/patologia , Rim/cirurgia
6.
J Indian Med Assoc ; 110(3): 187-8, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23029952

RESUMO

Gastric tuberculosis is mostly secondary to pulmonary tuberculosis. Primary and isolated gastric tuberculosis is very rare. A case of primary gastric tuberculosis of stomach in a 45-year-old female, known diabetic and hypertensive who presented to the hospital with epigastric pain and vomiting is being reported. Endoscopy showed a gastric ulcerated nodular lesion and biopsy showed tuberculous granuloma. Repeat endoscopy after a course of antituberculosis treatment showed minimal gastritis and complete resolution of the ulcerated nodular lesion.


Assuntos
Antituberculosos/uso terapêutico , Estômago/patologia , Tuberculose Gastrointestinal , Dor Abdominal/etiologia , Biópsia , Feminino , Gastroscopia/métodos , Humanos , Pessoa de Meia-Idade , Doenças Raras , Resultado do Tratamento , Tuberculose Gastrointestinal/complicações , Tuberculose Gastrointestinal/diagnóstico , Tuberculose Gastrointestinal/tratamento farmacológico , Tuberculose Gastrointestinal/fisiopatologia , Vômito/etiologia
7.
J Ethnopharmacol ; 142(1): 72-9, 2012 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-22855944

RESUMO

ETHNOPHARMACOLOGICAL RELEVANCE: Wrightia tomentosa Roem. & Schult. (Apocynaceae) is known in the traditional medicine for anti-cancer activity along with other broad indications like snake and scorpion bites, renal complications, menstrual disorders etc. However, the anti-cancer activity of this plant or its constituents has never been studied systematically in any cancer types so far. AIM OF THE STUDY: To evaluate the anti-cancer activities of the ethanolic extract of W. tomentosa and identified constituent active molecule(s) against breast cancer. MATERIAL AND METHODS: Powdered leaves of W. tomentosa were extracted with ethanol. The ethanolic extract, subsequent hexane fractions and fraction F-4 of W. tomentosa were tested for its anti-proliferative and pro-apoptotic effects in breast cancer cells MCF-7 and MDA-MB-231. RESULTS: The ethanolic extract, subsequent hexane fractions and fraction F-4 of W. tomentosa inhibited the proliferation of human breast cancer cell lines, MCF-7 and MDA-MB-231. The fraction F-4 obtained from hexane fraction inhibited proliferation of MCF-7 and MDA-MB-231 cells in concentration and time dependent manner with IC50 of 50 µg/ml and 30 µg/ml for 24 h, 28 µg/ml and 22 µg/ml for 48 h and 25 µg/ml and 20 µg/ml for 72 h respectively. The fraction F-4 induced G1 cell cycle arrest, reactive oxygen species (ROS) generation, loss of mitochondrial membrane potential and subsequent apoptosis. Apoptosis is indicated in terms of increased Bax/Bcl-2 ratio, enhanced Annexin-V positivity, caspase 8 activation and DNA fragmentation. The active molecule isolated from fraction F-4, oleanolic acid and urosolic acid inhibited cell proliferation of MCF-7 and MDA-MB-231 cells at IC50 value of 7.5 µM and 7.0 µM respectively, whereas there is devoid of significant cell inhibiting activity in non-cancer originated cells, HEK-293. In both MCF-7 and MDA-MB-231, oleanolic acid and urosolic acid induced cell cycle arrest and apoptosis as indicated by significant increase in Annexin-V positive apoptotic cell counts. CONCLUSION: Our results suggest that W. tomentosa extracts has significant anti-cancer activity against breast cancer cells due to induction of apoptosis pathway. Olenolic and urosolic acid are important constituent molecules in the extract responsible for anti-cancer activity of W. tomentosa.


Assuntos
Antineoplásicos/farmacologia , Apocynaceae , Ácido Oleanólico/farmacologia , Extratos Vegetais/farmacologia , Triterpenos/farmacologia , Apoptose/efeitos dos fármacos , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Ciclo Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Etanol/química , Células HEK293 , Humanos , L-Lactato Desidrogenase/metabolismo , Folhas de Planta , Solventes/química , Ácido Ursólico
8.
J R Coll Physicians Edinb ; 42(1): 24-6, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-22441059

RESUMO

Digital gangrene is not usually associated with primary Raynaud's phenomenon (RP). Its presence should therefore alert the healthcare provider to look for an alternative explanation. A 19-year-old female patient with primary RP developed digital gangrene following surgical management of acute paronychia. The possible mechanism in this patient appears to be the augmentation of the vasoconstrictive response due to the local infiltration of epinephrine mixed with lignocaine prior to the incision and drainage of her infected finger.


Assuntos
Doenças do Tecido Conjuntivo/diagnóstico , Epinefrina/efeitos adversos , Dedos/patologia , Gangrena/etiologia , Complicações Pós-Operatórias , Doença de Raynaud/diagnóstico , Vasoconstritores/efeitos adversos , Adulto , Procedimentos Cirúrgicos Dermatológicos , Feminino , Dedos/cirurgia , Humanos , Paroniquia/cirurgia , Doença de Raynaud/complicações , Pele/patologia , Vasoconstrição , Adulto Jovem
9.
Diabetes Metab ; 37(4): 312-7, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21917496

RESUMO

AIMS AND OBJECTIVES: Hand soft-tissue changes are well described in patients with T1DM, but not in T2DM patients. For this reason, this study aimed at examining the prevalence and pattern of hand soft-tissue changes in patients with T2DM. METHODS: A total of 206 consecutive patients with T2DM and 203 age-, gender- and occupation-matched healthy controls were examined by two individual observers, and then underwent the appropriate investigations. RESULTS: The 132 (64%) patients with T2DM included 187 hands compared with 96 (23.6%) healthy controls including 133 hands (P=0.01 for both). Dupuytren's contracture (DC) (42 vs. 29.3%, respectively; P=0.01), limited joint mobility (LJM) (39 vs. 28.5%, respectively; P=0.01) and carpal tunnel syndrome (CTS) (5.3 vs. 1%, respectively; P=0.01) were significantly higher in T2DM patients than in the controls, but not stenosing flexor tenosynovitis (FTS, 'trigger finger'). Indeed, none of the patients or controls had FTS. In patients with T2DM, DC showed a radial shift, and was more horizontal and severe than in the controls. These hand soft-tissue changes correlated significantly with age (P=0.0001), duration of diabetes (P=0.001) and the presence of microangiopathy (P=0.001). CONCLUSION: Hand changes are more prevalent and severe in patients with T2DM, and are correlated with age, duration of diabetes and microvascular complications.


Assuntos
Diabetes Mellitus Tipo 2/complicações , Articulação da Mão/patologia , Mãos/patologia , Adulto , Fatores Etários , Análise de Variância , Síndrome do Túnel Carpal/complicações , Síndrome do Túnel Carpal/epidemiologia , Estudos de Casos e Controles , Diabetes Mellitus Tipo 2/epidemiologia , Contratura de Dupuytren/complicações , Contratura de Dupuytren/epidemiologia , Feminino , Mãos/fisiopatologia , Articulação da Mão/fisiopatologia , Humanos , Masculino , Pessoa de Meia-Idade , Prevalência , Fatores de Risco , Estatísticas não Paramétricas , Dedo em Gatilho/complicações , Dedo em Gatilho/epidemiologia
10.
Nitric Oxide ; 25(3): 326-30, 2011 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-21741493

RESUMO

BACKGROUND: Polycystic ovary syndrome (PCOS) is associated with incremental risk of atherosclerosis and possibly of cardiovascular events. Insulin resistance (IR) occurs frequently in PCOS subjects, which might be one of the mechanisms involved in engendering such risk. We sought to evaluate whether the impact of other factors potentially associated both with PCOS and with IR might differentially modulate degree of IR in women with and without PCOS. METHODS AND RESULTS: We measured body mass index (BMI), hs-CRP, plasma concentrations of asymmetric dimethylarginine (ADMA), vitamin D (25(OH)D3) levels and platelet responsiveness to nitric oxide donor sodium nitroprusside (NO responsiveness) in 47 young women (n=27 with PCOS and n=20 weight-matched controls) without metabolic syndrome, hypertension or overt cardiovascular disease. We performed univariate and multivariate regression analyses to establish correlates of the quantitative insulin-sensitivity check index (QUICKI), as a marker of IR. On univariate analysis, plasma 25(OH)D3 levels and low NO responsiveness tended to be direct correlates with QUICKI in the entire subject group. BMI, hs-CRP, and ADMA levels were significant inverse correlates of QUICKI in PCOS subjects, but not in subjects without PCOS. On multivariate analysis, NO responsiveness, and 25(OH)D3 levels, but not PCOS per se were significant correlates of QUICKI. CONCLUSIONS: In the entire cohort of young women, low NO responsiveness and vitamin D deficiency are associated with low QUICKI, while elevated ADMA, inflammatory activation and obesity are selectively associated with low QUICKI in PCOS subjects; this may contribute to the increased cardiovascular risk associated with this syndrome.


Assuntos
Insulina/metabolismo , Óxido Nítrico/metabolismo , Síndrome do Ovário Policístico/metabolismo , Vitamina D/metabolismo , Adolescente , Adulto , Feminino , Humanos , Resistência à Insulina , Pessoa de Meia-Idade , Adulto Jovem
13.
Fitoterapia ; 81(7): 755-61, 2010 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-20388534

RESUMO

Evidences have suggested that Tectona grandis (TG) attenuates gastric mucosal injury; however its mechanism has not yet been established. The aim of present study was to evaluate the gastroprotective mechanism of ethanolic extract of TG (E-EtOH), butanolic fraction (Fr-Bu) and to identify its active constituents. Anti-ulcer activities were evaluated against cold restraint (CRU) and pyloric ligation (PL) induced gastric ulcer models and further confirmed through H(+) K(+)-ATPase inhibitory activity. Cytoprotective activity was evaluated in alcohol (AL) induced gastric ulcer model and further through PGE(2) level. E-EtOH and Fr-Bu attenuated ulcer formation in CRU. Moreover E-EtOH and Fr-Bu displayed potent anti-secretory activity as evident through reduced free acidity and pepsin activity in PL, confirmed further by in vitro inhibition of H(+) K(+)-ATPase activity. In addition cytoprotective potential of E-EtOH and Fr-Bu were apparent with protection in AL model, increased PGE(2) content and enhanced mucin level in PL. Phytochemical investigations of Fr-Bu yielded terpenoides and a phenolic glycoside, verbascoside. The anti-secretory mechanism of verbascoside mediated apparently through inhibition of H(+) K(+)-ATPase with corresponding decrease in plasma gastrin level, is novel to our finding. Gastroprotection elicited by TG might be through proton pump inhibition and consequent augmentation of the defensive mechanism.


Assuntos
Antiulcerosos/farmacologia , Glucosídeos/farmacologia , Fenóis/farmacologia , Extratos Vegetais/farmacologia , Inibidores da Bomba de Prótons , ATPase Trocadora de Sódio-Potássio/antagonistas & inibidores , Úlcera Gástrica/tratamento farmacológico , Verbenaceae/química , Animais , Antiulcerosos/isolamento & purificação , Antiulcerosos/uso terapêutico , Temperatura Baixa , Dinoprostona/metabolismo , Modelos Animais de Doenças , Feminino , Ácido Gástrico/metabolismo , Mucosa Gástrica/metabolismo , Gastrinas/sangue , Glucosídeos/análise , Glucosídeos/uso terapêutico , Masculino , Mucinas/metabolismo , Pepsina A/antagonistas & inibidores , Fenóis/análise , Fenóis/uso terapêutico , Fitoterapia , Extratos Vegetais/química , Extratos Vegetais/uso terapêutico , Folhas de Planta , Ratos , Ratos Sprague-Dawley , Estômago/efeitos dos fármacos , Úlcera Gástrica/metabolismo
14.
HPB (Oxford) ; 10(5): 363-70, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-18982153

RESUMO

UNLABELLED: OBJECTIVE & BACKGROUND DATA: Mortality following pancreatoduodenectomy (PD) has fallen below 5%, yet morbidity remains between 30 and 50%. Major haemorrhage following PD makes a significant contribution to this ongoing morbidity and mortality. The aim of the present study was to validate the new International Study Group of Pancreatic Surgery (ISGPS) Clinical grading system in predicting the outcome of post pancreaticoduodenectomy haemorrhage (PPH). MATERIAL AND METHODS: Between January 1998 and December 2007 a total of 458 patients who underwent Whipple's pancreaticoduodenectomy in our department were analysed with regard to haemorrhagic complications. The onset, location and severity of haemorrhage were classified according to the new criteria developed by an ISGPS. Risk factors for haemorrhage, management and outcome were analysed. RESULTS: Severe PPH occurred in 14 patients (3.1%). Early haemorrhage (<24 hours) was recorded in five (36%) patients, and late haemorrhage (>24 hours) in nine (64%) patients. As per Clinical grading of ISGPS 7 (50%) belongs to Grade C and 7 (50%) belongs to Grade B. Haemostasis was attempted by surgery in 10 (71%) patients; angioembolisation was successful in two (14%) and endotherapy in one (7%) patient. The overall mortality is 29%(n=4). Age >60 years (p=0.02), sentinel bleeding (p=0.04), pancreatic leak (p=0.04) and ISGPS Clinical grade C (p=0.02) were associated with increased mortality. CONCLUSION: Early haemorrhage was mostly managed surgically with better outcome when endoscopy is not feasible. Late haemorrhage is associated with high mortality due to pancreatic leak and sepsis. ISGPS Clinical grading of PPH is useful in predicting the outcome.

17.
World J Surg ; 30(8): 1507-18; discussion 1519, 2006 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-16865318

RESUMO

BACKGROUND: In Japan, the original Sugiura procedure reported favorable results in non-cirrhotic patients but in the West, the modified Sugiura procedure is not widely accepted because of high rebleeding, morbidity, and mortality in cirrhotics. We retrospectively analyzed the efficacy of our modified Sugiura procedure i.e., devascularization with/without esophageal transection combined with salvage endotherapy and pharmacotherapy for control of a variceal bleed. MATERIALS AND METHODS: Between January 1999 and December 2004, 912 patients with variceal bleeding were treated. Of these, 66 (7.2%) patients were subjected to surgery after failed endotherapy/propranolol. Among these 66 patients, 52 had transabdominal devascularization (16 emergency, 36 elective); 14 patients underwent devascularization with esophageal stapler transection (group I), and 38 patients had devascularization without esophageal stapler transection (group II). Another 14 patients underwent elective end-to-side proximal splenorenal shunt surgery. RESULTS: Postoperative mortality was 7.1% in group I, 10.5% in group II (P>0.05). Mortality for emergency surgery was 31.2% (5/16) but there were no deaths in the elective surgery group. Overall morbidity was 57.1% in group I and 21.0% in group II (P<0.05). The rates of variceal rebleeding were 7.1% and 7.8%; residual varices were 30.7% and 32.3%; recurrent varices were 7.6% and 5.8% following the group I and group II procedures, respectively, over a mean follow-up period of 39.9 (7-2) months. Esophageal transection-related morbidity (leak, stricture, and bleeding) was 21.4% (3/14) in group I. CONCLUSIONS: Devascularization without esophageal stapler transection is a safe and effective procedure for adequate (urgent and long-term) control of variceal bleeding with similar results and less morbidity when compared to devascularization with esophageal transection in cirrhotic patients, as well as non-cirrhotic patients.


Assuntos
Procedimentos Cirúrgicos do Sistema Digestório/métodos , Varizes Esofágicas e Gástricas/cirurgia , Esôfago/cirurgia , Hemorragia Gastrointestinal/cirurgia , Prevenção Secundária , Grampeamento Cirúrgico , Adulto , Idoso , Varizes Esofágicas e Gástricas/complicações , Feminino , Hemorragia Gastrointestinal/etiologia , Humanos , Masculino , Pessoa de Meia-Idade , Resultado do Tratamento
18.
19.
J Mol Biol ; 303(5): 773-95, 2000 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-11061975

RESUMO

The kinetic mechanism of DNA-independent binding and hydrolysis of ATP by the E. coli replicative helicase DnaB protein has been quantitatively examined using the rapid quench-flow technique. Single-turnover studies of ATP hydrolysis, in a non-interacting active site of the helicase, indicate that bimolecular association of ATP with the site is followed by the reversible hydrolysis of nucleotide triphosphate and subsequent conformational transition of the enzyme-product complex. The simplest mechanism, which describes the data, is a three-step sequential process defined by:¿eqalign¿¿¿rm Helicase+ATP¿&¿mathop¿¿rightleftharpoons¿ ¿k_1¿_¿k_¿-1¿¿¿¿rm (H-ATP)¿¿mathop¿¿rightleftharpoons¿ ¿k_2¿_¿k_¿-2¿¿¿¿rm (H-ADP¿cdot Pi)¿¿cr &¿mathop¿¿rightleftharpoons¿ ¿k_3¿_¿k_¿-3¿¿¿¿rm (H-ADP¿cdot Pi)¿ *¿The sequential character of the mechanism excludes conformational transitions of the DnaB helicase prior to ATP binding. Analysis of relaxation times and amplitudes of the reaction allowed us to estimate all rate and equilibrium constants of partial steps of the proposed mechanism. The intrinsic binding constant for the formation of the (H-ATP) complex is K(ATP)=(1.3+/-0.5)x10(5) M(-1). The analysis of the data indicates that a part of the ATP binding energy originates from induced structural changes of the DnaB protein-ATP complex prior to ATP hydrolysis. The equilibrium constant of the chemical interconversion is K(H)=k(2)/k(-2) approximately 2 while the subsequent conformational transition is characterized by K(3)=k(3)/k(-3) approximately 30. The low value of K(H) and the presence of the subsequent energetically favorable conformational step(s) strongly suggest that free energy is released from the enzyme-product complex in the conformational transitions following the chemical step and before the product release.The combined application of single and multiple-turnover approaches show that all six nucleotide-binding sites of the DnaB hexamer are active ATPase sites. Binding of ATP to the DnaB hexamer is characterized by the negative cooperativity parameter sigma=0.25(+/-0.1). The negative cooperative interactions predominantly affect the ground state of the enzyme-ATP complex. The significance of these results for the mechanism of the free energy transduction of the DnaB helicase is discussed.


Assuntos
Adenosina Trifosfatases/metabolismo , Trifosfato de Adenosina/metabolismo , Proteínas de Bactérias , DNA Helicases/metabolismo , DNA/metabolismo , Escherichia coli/enzimologia , Adenosina Trifosfatases/química , Bacteriófago T7/enzimologia , Sítios de Ligação , Catálise , Simulação por Computador , DNA/genética , DNA Helicases/química , DnaB Helicases , Hidrólise , Cinética , Ligação Proteica , Estrutura Quaternária de Proteína , Termodinâmica
20.
Biochemistry ; 39(42): 12959-69, 2000 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-11041861

RESUMO

Quantitative analyses of the interactions of nucleotide cofactors with the Escherichia coli replicative factor DnaC protein have been performed using thermodynamically rigorous fluorescence titration techniques. This approach allowed us to obtain stoichiometries of the formed complexes and interaction parameters, without any assumptions about the relationship between the observed signal and the degree of binding. The stoichiometry of the DnaC-nucleotide complex has been determined in direct binding experiments with fluorescent nucleotide analogues, MANT-ATP and MANT-ADP. The stoichiometry of the DnaC complexes with unmodified ATP and ADP has been determined using the macromolecular competition titration method (MCT). The obtained results established that at saturation the DnaC protein binds a single nucleotide molecule per protein monomer. Analyses of the binding of fluorescent analogues and unmodified nucleotides to the DnaC protein show that ATP and ADP have the same affinities for the nucleotide-binding site, albeit the corresponding complexes have different structures, specifically affected by the presence of magnesium cations in solution. Although the presence of the gamma-phosphate does not affect the affinity, the structure of the triphosphate group is critical. While the affinity of ATP-gamma-S is the same as the affinity of ATP, the affinities of AMP-PNP and AMP-PCP are approximately 2 and approximately 4 orders lower than that of ATP, respectively. Moreover, the ribose plays a significant role in forming a stable complex. The binding constants of dATP and dADP are approximately 2 orders of magnitude lower than those for ribose nucleotides. The nucleotide-binding site of the DnaC protein is highly base specific. The intrinsic affinity of adenosine triphosphates and diphosphates is at least 3-4 orders of magnitude higher than for any of the other examined nucleotides. The obtained data indicate that the recognition mechanism of the nucleotide by the structural elements of the binding site is complex with the base providing the specificity and the ribose, as well as the second phosphate group contributing to the affinity. The significance of the results for the functioning of the DnaC protein is discussed.


Assuntos
Difosfato de Adenosina/análogos & derivados , Trifosfato de Adenosina/análogos & derivados , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Proteínas de Escherichia coli , Nucleotídeos/química , Nucleotídeos/metabolismo , Adenosina/química , Difosfato de Adenosina/química , Difosfato de Adenosina/metabolismo , Trifosfato de Adenosina/química , Trifosfato de Adenosina/metabolismo , Marcadores de Afinidade/química , Ligação Competitiva , Brometos/química , Replicação do DNA , Escherichia coli , Corantes Fluorescentes/química , Substâncias Macromoleculares , Cloreto de Magnésio/química , Ribose/química , Cloreto de Sódio/química , Compostos de Sódio/química , Fosfatos Açúcares/química , ortoaminobenzoatos/química
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