RESUMEN
Objective: To investigates the clinical efficacy of the trabecular metal acetabular revision system (TMARS) in one-stage reconstruction of acetabular deficiencies associated with periprosthetic joint infection (PJI). Methods: This is a retrospective case series study,including the data of 59 patients with PJI underwent acetabular defect reconstruction by TMARS during one-stage revisions in the Department of Orthopaedics, the First Affiliated Hospital of Xinjiang Medical University from January 2013 to December 2021. There were 32 males and 27 females, aged (59.5±14.6) years (range: 26 to 84 years). Among them, 29 cases used tantalum cups, 13 cases used tantalum cups and tantalum reinforcing blocks, 9 cases used cup-cage, and 8 cases used multi-cup reconstruction techniques. The surgery procedure, Harris Hip score (HHS), recovery of the hip rotation center, implant survival rate, postoperative reinfection rate, and complications were recorded. Data were compared using the Wilcoxon rank-sum test. Results: All of the 59 patients underwent the operations successfully. Operation time was (188.9±48.4) minutes (range: 110 to 340 minutes), and intraoperative bleeding volume was (M(IQR)) 1 000(400)ml (range: 600 to 1 800 ml). After a postoperative follow-up of 5.1 (2.6) years (range: 2.0 to 10.5 years), the prosthesis survival rate was 94.9% (56/59). Recurrence of infection occurred in 3 cases (5.1%), aseptic loosening in 1case(1.7%), and hip dislocation in 4 cases (6.8%). At the last follow-up, HHS improved significantly(84 (12) vs. 44 (9), Z=-6.671, P<0.01), and the center of rotation of the hips were recovered in all cases. Conclusions: In one-stage revision surgeries aimed at reconstructing acetabular defects, utilizing the TMARS can provide stable initial fixation, restore a more natural center of rotation, significantly enhance early postoperative hip joint function, and reduce the likelihood of infection recurrence. This approach stands as a reliable choice for addressing acetabular defects during revision surgeries for infected hip joints.
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Acetábulo , Artroplastia de Reemplazo de Cadera , Infecciones Relacionadas con Prótesis , Reoperación , Humanos , Femenino , Persona de Mediana Edad , Masculino , Estudios Retrospectivos , Anciano , Infecciones Relacionadas con Prótesis/cirugía , Acetábulo/cirugía , Adulto , Anciano de 80 o más Años , Artroplastia de Reemplazo de Cadera/métodos , Prótesis de Cadera , Resultado del Tratamiento , Procedimientos de Cirugía Plástica/métodos , MetalesRESUMEN
Objective: To explore the status of seroepidemiology on hepatitis A, B and C among students and residents aged equal or greater than 18 years in south Xinjiang, and to provide scientific evidence for prevention and control of viral hepatitis. Methods: Uyghur students in four towns and villages were selected by cluster random sampling from Feb to May, 2015, and Uyghur residents aged 18 to 69 years were selected by stratified cluster sampling from May to September, 2016. 4 507 middle and primary Uygur students and 4 833 Uyghur resides equal or greater than 18 years attended this survey. Self-designed questionnaire was used to collect the demographic information. And Elisa test was adopted to detect HAV-IgG, HBsAg, HBsAb and HCV-IgG. Chi-square test was used to calculate the difference on antibody positive rate of three types of hepatitis among the participants. Results: The overall HAV-IgG positive rate was 99.45% (9 289/9 340). The positive rates were 99.70% (4 006/4 018) in male and 99.27% (5 283/5 322) in female (χ(2)=7.95, P=0.005). The HAV-IgG positive rate among people aged 10 to 14 years was the highest (99.91%, 2 233/2 235), and the difference between the age specific HAV-IgG positive rates was statistical significant (χ(2)=38.21, P<0.001). The overall HBsAg positive rate was 4.11% (384 cases), with 4.55% (183 cases) for male and 3.78% (201 cases) for female. The HBsAg positive rate among participants 19 to 24 years old was the highest (9.46%, 21/222) and the differences between the age specific HBsAg was statistically significant (χ(2)=116.22, P<0.001). The HBsAb positive rate was 35.03% (3 272 cases), with 35.59% (1 430 cases) for male and 34.61% (1 842 cases) for female, and the HBsAb positive rate among participants aged 15 to 18 years was the highest, which was 69.12% (696/1 007). The differences between the age specific HBsAb rates appeared statistically significant (χ(2)=671.80, P<0.001). The overall HCV-IgG positive rate was 0.65%(61 cases). The HCV-IgG positive rate in female was 0.86% (46 cases) and 0.37% (15 cases) in male (χ(2)=8.51, P=0.004).The HCV-IgG positive rate among participants aged over 70 years was the highest (3.78%,9/238) , and the difference between the age specific HCV-IgG positive rates had statistic significance (χ(2)=70.30, P<0.001). The HAV-IgG positive rate in hepatitis A vaccinees (100%, 876/876) was higher than that among the non-vaccinees (99.40%, 8 413/8 464) (χ(2)=4.26, P=0.039). The HBsAb positive rate in hepatitis B vaccinees was 39.32% (1 816/4 619) which was higher than that among the non-vaccinees (30.84%, 1 456/4 721) (χ(2)=73.68, P<0.001). Conclusion: The positive rate of overall HAV-IgG was high, male and participants aged between 10 to 14 had higher probability to be infected. But the infection rates of hepatitis B and C were low, with the low vaccination rate and the poor protective effectiveness of hepatitis B.
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Anticuerpos Antiidiotipos/inmunología , Anticuerpos Antivirales/inmunología , Anticuerpos Antihepatitis/sangre , Hepatitis Viral Humana/epidemiología , Adolescente , Adulto , Anciano , Anticuerpos Antivirales/sangre , Niño , China/epidemiología , Estudios Transversales , Ensayo de Inmunoadsorción Enzimática , Femenino , Hepatitis A/epidemiología , Hepatitis A/inmunología , Anticuerpos Antihepatitis/clasificación , Anticuerpos Antihepatitis/inmunología , Hepatitis B/epidemiología , Hepatitis B/inmunología , Anticuerpos contra la Hepatitis B , Antígenos de Superficie de la Hepatitis B , Humanos , Masculino , Persona de Mediana Edad , Estudios Seroepidemiológicos , Estudiantes , Encuestas y Cuestionarios , VacunaciónRESUMEN
We previously identified a protein (p67) in the yeast, Saccharomyces cerevisiae, that specifically recognizes nuclear localization sequences. We report here the partial purification of p67, and the isolation, sequencing, and disruption of the gene (NSR1) encoding this protein. p67 was purified using an affinity column conjugated with a peptide containing the histone H2B nuclear localization sequence from yeast. Using antibodies against p67 we have cloned the gene for this protein. The protein encoded by the NSR1 gene recognizes the wild-type H2B nuclear localization sequence, but does not recognize a mutant H2B sequence that is incompetent for nuclear localization in vivo. Interestingly, the NSR1 protein has two RNA recognition motifs, as well as an acidic NH2 terminus containing a series of serine clusters, and a basic COOH terminus containing arg-gly repeats. We have confirmed the nuclear localization of p67 by immunofluorescence and found that a restricted portion of the nucleus is highlighted. We have also shown that NSR1 (p67) is required for normal cell growth.
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Proteínas Fúngicas/genética , Genes Fúngicos , Membrana Nuclear/química , Proteínas Nucleares/metabolismo , Receptores de Superficie Celular/genética , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/genética , Secuencia de Aminoácidos , Secuencia de Bases , Proteínas Portadoras/química , Proteínas Portadoras/genética , Proteínas Portadoras/aislamiento & purificación , Compartimento Celular , Cromatografía de Afinidad , Clonación Molecular , Análisis Mutacional de ADN , ADN de Hongos/genética , Técnica del Anticuerpo Fluorescente , Proteínas Fúngicas/inmunología , Proteínas Fúngicas/aislamiento & purificación , Proteínas Fúngicas/metabolismo , Datos de Secuencia Molecular , Peso Molecular , Biosíntesis de Proteínas , ARN/metabolismo , Proteínas de Unión al ARN , Receptores de Superficie Celular/aislamiento & purificación , Receptores de Superficie Celular/metabolismo , Transcripción GenéticaRESUMEN
BACKGROUND: Pancreatic cancer (PC) is a highly aggressive and metastatic disease, with an elevated mortality rate. It is, therefore, crucial to assess factors affecting the prognosis of PC patients. Meanwhile, calpain-1 is associated with malignant tumor progression and metastasis. Thus, it is meaningful to evaluate the relationship between calpain-1 and PC. MATERIALS AND METHODS: Calpain-1 protein expression was assessed by immunohistochemistry in 96 pancreatic cancer samples and paired adjacent non-cancerous specimens. In addition, calpain-1 protein levels were assessed in six PC cell lines by western blot (WB). Next, PC cells were transfected with calpain-1 siRNA, and silencing was confirmed by WB. Finally, cell proliferation, colony formation, migration and invasion assays, and cell apoptosis analysis were performed to examine the effects of calpain-1 knockdown on proliferation, growth, apoptosis, migration, and invasion in PC cells. RESULTS: The results showed that calpain-1 was overexpressed in PC tissues and cells. Meanwhile, calpain-1 overexpression was associated with tumor site (P = 0.029), metastasis (P = 0.000), and TNM stage (P = 0.000), but showed no associations with histological grade (P = 0.396), age (P = 0.809), sex (P = 1.000), and lesion size (P = 0.679). The Kaplan-Meier method demonstrated that the low calpain-1 expression group had increased overall survival (OS) compared with patients expressing high calpain-1 levels (28.7 ± 4.1 vs. 17.0 ± 2.3 months) (P = 0.005). Besides, calpain-1 in PC cells was successfully silenced by liposome-mediated RNA interference, resulting in reduced cell growth, invasion, and metastasis in PC cells, with no effect on apoptosis. CONCLUSION: The above findings suggest that calpain-1 should be considered a potential biomarker for PC prognosis and therapy.
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Biomarcadores de Tumor/metabolismo , Calpaína/metabolismo , Carcinoma Ductal Pancreático/mortalidad , Proliferación Celular , Pancreatectomía/mortalidad , Neoplasias Pancreáticas/mortalidad , Apoptosis , Biomarcadores de Tumor/genética , Calpaína/genética , Carcinoma Ductal Pancreático/metabolismo , Carcinoma Ductal Pancreático/secundario , Carcinoma Ductal Pancreático/cirugía , Estudios de Casos y Controles , Ciclo Celular , Movimiento Celular , Progresión de la Enfermedad , Femenino , Estudios de Seguimiento , Regulación Neoplásica de la Expresión Génica , Humanos , Metástasis Linfática , Masculino , Persona de Mediana Edad , Invasividad Neoplásica , Neoplasias Pancreáticas/metabolismo , Neoplasias Pancreáticas/patología , Neoplasias Pancreáticas/cirugía , Pronóstico , Tasa de Supervivencia , Células Tumorales CultivadasRESUMEN
Objective: To understand the prevalence of dyslipidemia and normal blood lipids level in Uygur diabetes patients in Kashgar prefecture in southern area of Xinjiang. Methods: A total of 5 078 local residents aged ≥18 years (42.56% were men) selected through cluster random sampling in Kashgar were surveyed by means of questionnaire survey, physical examination and laboratory test, and 521 diabetes patients were screened. Results: The overall prevalence of dyslipidemia in diabetes patients was 59.50% (310/521) with adjusted rate as 49.39%. Age ≥65 years, overweight, obesity and abdominal obesity increased the risk for dyslipidemia by 0.771 times (95% CI: 1.015-3.088), 1.132 times (95% CI: 1.290-3.523), 1.688 times (95% CI: 1.573-4.592) and 0.801 times (95% CI: 1.028-3.155) respectively. Compared with males, female was a protective factor for dyslipidemia (OR=0.507, 95%CI: 0.334-0.769). The overall normal rate of blood lipids level including total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) for type 2 diabetes patients was 11.13%. Female, higher BMI and abdominal obesity were the factors influencing the overall normal blood lipids level. The normal rate of LDL-C level decreased with increase of age, BMI and waist circumferences (trend test χ(2)=18.049, P<0.001; trend test χ(2)=10.582, P=0.001; χ(2)=19.081, P<0.001), but increased with educational level (trend test χ(2)=9.764, P=0.002). Conclusion: The prevalence of dyslipidemia in Uygur diabetes patients in Kashgar was high, however, the overall normal rate of blood lipid level was relatively low. Obesity was the most important risk factor for dyslipidemia in this area. More attention should be paid to dyslipidemia prevention in women.
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Dislipidemias/epidemiología , Etnicidad/estadística & datos numéricos , Lípidos/sangre , Adulto , Anciano , China/epidemiología , Colesterol/sangre , HDL-Colesterol/sangre , LDL-Colesterol/sangre , Diabetes Mellitus Tipo 2/epidemiología , Diabetes Mellitus Tipo 2/etnología , Dislipidemias/etnología , Femenino , Humanos , Lipoproteínas HDL , Masculino , Persona de Mediana Edad , Obesidad/epidemiología , Obesidad/etnología , Obesidad Abdominal , Sobrepeso , Prevalencia , Factores de Riesgo , Encuestas y Cuestionarios , Triglicéridos/sangre , Circunferencia de la CinturaRESUMEN
Objective: To investigate the epidemiologic characteristics of diabetes mellitus (DM) in Uygur residents in Kashgar of Xinjiang. Methods: The survey was conducted among the Uygur residents aged ≥18 years selected through stratified cluster sampling in Kashgar by means of questionnaire survey, physical examination and basic laboratory test. The prevalence of different groups were calculated and risk factors of DM was analyzed by logistic vegression model. Results: A total of 4 608 adults were surveyed. The prevalence of DM was 11.31% (standardized prevalence: 10.59%) and the prevalence was 13.65% (standardized prevalence: 12.34%) in males and 10.04% (standardized prevalence: 9.83%) in females. The prevalence increased with age. The prevalence of DM was higher than the prevalence of impaired fasting glucose (IFG) in people aged >60 years, especially in females. The rates of awareness, treatment and control of DM were 28.02%, 21.31% and 5.57%, respectively. Multivariate logistic regression analysis indicated that people aged 45-55, 55-65 and >65 years had higher risk of DM and the odds ratio were 2.08 (95%CI: 1.24-3.48), 2.73 (95%CI: 1.63-4.56) and 3.90 (95%CI: 2.24-6.78) for men and 2.63 (95% CI: 1.71-4.02), 3.14 (95%CI: 2.00-4.94) and 5.56 (95%CI: 3.47-8.92) for woman, respectively. Family history of DM (OR=2.88 for men, 95% CI: 1.45-5.72; OR=2.52 for women, 95% CI: 1.49-4.26) and BMI≥28.0 kg/m(2) (OR=1.77 for men, 95% CI: 1.19-2.64, OR=1.80 for women, 95% CI: 1.30-2.50) were also risk factors for DM. Conclusion: The prevalence of DM was high in Uygur residents in Kashgar, but the rate of awareness, treatment and control of DM were low. It is necessary to improve the detection rate of DM and conduct targeted prevention and control of DM.
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Diabetes Mellitus/epidemiología , Etnicidad/estadística & datos numéricos , Conocimientos, Actitudes y Práctica en Salud , Estado Prediabético/epidemiología , Adulto , Anciano , Pueblo Asiatico/etnología , Concienciación , China/epidemiología , Diabetes Mellitus/etnología , Diabetes Mellitus/etiología , Femenino , Humanos , Modelos Logísticos , Masculino , Persona de Mediana Edad , Estado Prediabético/etnología , Estado Prediabético/etiología , Prevalencia , Factores de Riesgo , Encuestas y CuestionariosRESUMEN
Objective: To investigate the knowledge, attitude and practice (KAP) to chronic diseases and associated influencing factors in Uygur adults in Kashgar of southern Xinjiang, and provide basic information for developing ethnic specific prevention and control strategies for chronic diseases. Methods: With stratified cluster random sampling, investigations, including questionnaire survey, physical examination and laboratory tests were performed among local residents who were aged ≥18 years and selected in Shufu county in southern Xinjiang. KAP scores were calculated and unconditional logistic regression models were used to analyze influencing factors. Results: A total of 4 772 Uygur adults were surveyed. The awareness rate of chronic disease related knowledge ranged from 4.32% to 56.04%, while the awareness rate of preventive measures were from 1.76% to 85.18% and the participation rate of prevention program varied from 4.00% to 97.99%. The average KAP score was 15.90±4.20 and the rate of total KAP was 47.86%. Multi-factor analysis suggested the pass rate of total KAP score increased with educational level. Other factors positively associated with 'KAP score pass rate' were commercial insurance investment, hypertension, family history of common chronic diseases, female and abdominal obesity, while overweight was negatively associated with the KAP score pass rate. Conclusions: The KAP level on chronic diseases was low in Uygur adults in Kashgar. It is necessary to continuously implement ethnic targeted health education and health promotion campaigns, especially in low education level, low income level, overweight and male groups.
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Enfermedad Crónica/epidemiología , Etnicidad/estadística & datos numéricos , Conocimientos, Actitudes y Práctica en Salud , Adulto , Pueblo Asiatico , China/epidemiología , Enfermedad Crónica/etnología , Femenino , Humanos , Hipertensión/epidemiología , Hipertensión/etnología , Masculino , Persona de Mediana Edad , Obesidad Abdominal , Sobrepeso , Factores de Riesgo , Clase Social , Encuestas y CuestionariosRESUMEN
Objective: To investigate the prevalence of hypertension and risk factors in Uygur adults in Kashgar of Xinjiang. Methods: A total of 4 748 Uygur adults aged ≥18 years selected through cluster random sampling in Shufu county of Kashgar prefecture were surveyed by means of questionnaire survey, physical examination and laboratory test. The prevalence, awareness, treatment and control rate of hypertension of different groups were calculated and risk factors of hypertension was analyzed by using non-conditional logistic regression model. Results: The overall prevalence of hypertension was 15.73% (age-adjusted prevalence was 13.75%). The prevalence rates of hypertension in men and women were 16.36% (age-adjusted prevalence was 12.96%), 15.39% (age-adjusted prevalence was 14.34%), respectively. The rates of awareness, treatment and control of hypertension were 59.57%, 52.74%, 21.29%, respectively. The prevalence of hypertension increased with age. Compared with age group 18-34 years, the age groups 55-64, ≥65 years had higher risk of hypertension and the OR values were 10.53, 20.96 for men and 16.27, 33.20 for women. The overweight (OR=1.47 for men, OR=1.82 for women, P<0.05) and obesity (OR=1.88 for men, OR=2.66 for women, P<0.05) also increased the risk of hypertension. The groups with family history of hypertension (OR=3.85 for men, OR=2.34 for women, P<0.05) also had higher risk of hypertension. Hypertriglyceridemia was positively correlated with the prevalence of hypertension in men (OR=1.62, 95%CI: 1.09-2.41). Conclusions: The prevalence of hypertension in Uygur adults in Kashgar area of Xinjiang was at relatively low level. The related risk factors were age, overweight, obesity, family history and hypertriglyceridemia in men and the risk factors were similar in women except hypertriglyceridemia.
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Etnicidad/estadística & datos numéricos , Hipertensión/epidemiología , Adulto , Anciano , Pueblo Asiatico , China/epidemiología , Femenino , Humanos , Hipertensión/etnología , Hipertrigliceridemia , Masculino , Persona de Mediana Edad , Obesidad/epidemiología , Obesidad/etnología , Sobrepeso , Prevalencia , Factores de Riesgo , Encuestas y CuestionariosRESUMEN
Objective: To explore the status of seroepidemiology on hepatitis A, B and C in primary and middle school students in Shufu county, Xinjiang Uygur Autonomous Region of China (Xinjiang) and to evaluate the effect of related immunization. Methods: Students in four towns and villages were selected by cluster random sampling method. HAV-IgG, HBsAg, HBsAb and HCV-IgG were detected in Feb to May, 2015. Results: The overall HAV-IgG positive rate was 99.75%, among 4 830 primary and middle school students. The positive rates were seen 99.92% in boys and 99.57% in girls, with difference statistically significant (χ2=5.798, P=0.016). The overall HBsAg positive rate appeared as 3.02%, with 3.55% for boys and 2.47% for girls, with difference statistically significant (χ2=4.782, P=0.029). The difference between age specific HBsAg positive rates also showed statistically significant (χ2=71.990,P=0.000). HBsAg positive rate in the students in rural area (3.28%) was higher than that in the students in urban area (1.61%, χ2=6.019, P=0.014). HBsAb positive rate was 38.84%, and the differences between the age specific HBsAb positive rates appeared statistically significant (χ2=837.699, P=0.000). HBsAg positive rate in students from the urban area (42.36%) was higher than those from the rural area (38.20%, χ2=4.598, P=0.032). 2 815 students, accounting for 58.28% of the total students, showed negative on both HBsAg and HBsAb. The overall HCV-IgG positive rate was 0.19%, and all appeared in students from the rural areas, with ethnicity solely as Uygur. Conclusions: The effect of hepatitis A vaccine was satisfactory in primary and middle school students in Shufu county but quiet a number of the students missed the vaccination. The infection rate of hepatitis C was low. Publicity and health education on hepatitis immunization and control should be revved up. Programs regarding primary and supplementary immunization on hepatitis, should be carried out timely for children of school age.
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Hepatitis A , Hepatitis B , Hepatitis C , China , Femenino , Vacunas contra la Hepatitis A , Anticuerpos contra la Hepatitis B , Antígenos de Superficie de la Hepatitis B , Humanos , Masculino , Instituciones Académicas , Estudios Seroepidemiológicos , Estudiantes , VacunaciónRESUMEN
Exposure of chloroplast F1 ATPase to 2-azido-ATP results in the noncovalent tight binding of 2-azido-ATP or 2-azido-ADP to noncatalytic or to catalytic sites. Subsequent photolysis results in covalent labeling of adjacent tryptic peptides of the beta-subunit. Binding at noncatalytic sites results in labeling of tyrosine 385 by an ATP or an ADP moiety. Binding at catalytic sites results in labeling of tyrosine 362 by only an ADP moiety. Similar labeling patterns are observed for the heat-activated or the membrane-bound enzymes.
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Nucleótidos de Adenina/metabolismo , Cloroplastos/enzimología , ATPasas de Translocación de Protón/metabolismo , Adenosina Difosfato/metabolismo , Adenosina Trifosfato/metabolismo , Marcadores de Afinidad , Sitios de Unión , Fragmentos de Péptidos/análisis , Mapeo Peptídico , FotoquímicaRESUMEN
Twenty patients of cholelithiasis underwent intraoperative transcystic duct fiberendoscopy in whom choledochotomy was otherwise indicated. Among them choledocholithotomy was done endoscopically in three patients and auxiliary choledocho-cystic junction incision was obligatory for easy insertion of the fiberscope in six. No T-tube was needed after the procedure and the postoperative recovery was uneventful in all cases.
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Colelitiasis/cirugía , Adulto , Anciano , Anciano de 80 o más Años , Colecistectomía , Conducto Colédoco/cirugía , Conducto Cístico , Endoscopía del Sistema Digestivo/métodos , Femenino , Humanos , Masculino , Persona de Mediana Edad , Procedimientos Quirúrgicos Operativos/métodosRESUMEN
Dry socket is one of the most frequent complications after teeth extraction,especially in impacted mandibular third molars.The etilogy and prevention is not clear.This study id based on principles of clinical epidemiology.Randomized double-blind method was carried out in 549 patients to test the value of the prophylactic use of Hydroxyapatite,to test the value of the prophylactic use of Hydroxyapatite and Metronidazole,placed in the sockets of extracted impacted mandibular third molars.The results of the incidence of DS was 7.1% of Metronidazole treated sockets,and 2.1% of Hydroxyapatite treated sockets,It is concluded that Hydroxyapatite is an effective preventive factor for dry socket,The possible mechanism of Hydroxyapatite and the dry socket etiology were discussed.
RESUMEN
Mg2+ is known to be a potent inhibitor of F1 ATPases from various sources. Such inhibition requires the presence of a tightly bound ADP at a catalytic site. Results with the spinach chloroplast F1 ATPase (CF1) show that the time delays of up to 1 min or more in the induction or the relief of the inhibition are best explained by a slow binding and slow release of Mg2+ rather than by slow enzyme conformational changes. CF1 is known to have multiple Mg2+ binding sites with Kd values in the micromolar range. The inhibitory Mg2+ and ADP can bind independently to CF1. When Mg2+ and ATP are added to the uninhibited enzyme, a relatively fast rate of hydrolysis attained soon after the addition is followed by a much slower steady-state rate. The inhibited steady-state rate results from a slowly attained equilibrium of binding of medium Mg2+. The Kd for the binding of the inhibitory Mg2+ is in the range of 1-8 microM, in the presence or absence of added ATP, as based on the extent of rate inhibition induced by Mg2+. Assessments from 18O exchange experiments show that the binding of Mg2+ is accompanied by a relatively rapid change to an enzyme form that is incapable of hydrolyzing MgATP. When ATP is added to the Mg2+- and ADP-inhibited enzyme, the resulting reactivation can be explained by MgATP binding to an alternate catalytic site which results in a displacement of the tightly bound ADP after a slow release of Mg2+. Both an increase in temperature (to 50 degrees C) and the presence of activating anions such as bicarbonate or sulfite reduce the extent of the Mg2+ inhibition markedly. The activating anions may bind to CF1 in place of Pi near the ADP. Whether the inhibitory Mg2+ binds at catalytic or noncatalytic nucleotide binding sites or at another location is not known. The Mg2(+)- and ADP-induced inhibition appears to be a general property of F1 ATPases, which show considerable differences in affinity for ADP, Mg2+, and Pi. These differences may reflect physiological control functions.
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ATPasa de Ca(2+) y Mg(2+)/antagonistas & inhibidores , Cloroplastos/enzimología , Magnesio/farmacología , Plantas/enzimología , ATPasas de Translocación de Protón/metabolismo , Guanosina Difosfato/farmacología , Cinética , Magnesio/metabolismo , Unión Proteica , ATPasas de Translocación de Protón/antagonistas & inhibidores , TermodinámicaRESUMEN
Whether the tightly bound ADP that can cause a pronounced inhibition of ATP hydrolysis by the chloroplast ATP synthase and F1 ATPase (CF1) is bound at catalytic sites or at noncatalytic regulatory sites or both has been uncertain. We have used photolabeling by 2-azido-ATP and 2-azido-ADP to ascertain the location, with Mg2+ activation, of tightly bound ADP (a) that inhibits the hydrolysis of ATP by chloroplast ATP synthase, (b) that can result in an inhibited form of CF1 that slowly regains activity during ATP hydrolysis, and (c) that arises when low concentrations of ADP markedly inhibit the hydrolysis of GTP by CF1. The data show that in all instances the inhibition is associated with ADP binding without inorganic phosphate (Pi) at catalytic sites. After photophosphorylation of ADP or 2-azido-ADP with [32P]Pi, similar amounts of the corresponding triphosphates are present on washed thylakoid membranes. Trials with appropriately labeled substrates show that a small portion of the tightly bound 2-azido-ATP gives rise to covalent labeling with an ATP moiety at noncatalytic sites but that most of the bound 2-azido-ATP gives rise to covalent labeling by an ADP moiety at a catalytic site. We also report the occurrence of a 1-2-min delay in the onset of the Mg2+-induced inhibition after addition of CF1 to solutions containing Mg2+ and ATP, and that this delay is not associated with the filling of noncatalytic sites. A rapid burst of Pi formation is followed by a much lower, constant steady-state rate.(ABSTRACT TRUNCATED AT 250 WORDS)
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Adenosina Difosfato/metabolismo , Adenosina Trifosfato/metabolismo , ATPasas de Translocación de Protón/metabolismo , Sitios de Unión , Cloroplastos/enzimología , Cromatografía Líquida de Alta Presión , Activación Enzimática , Guanosina Trifosfato/metabolismo , Magnesio/farmacologíaRESUMEN
When heat-activated F1-ATPase from chloroplasts was repeatedly exposed to Mg2+ and 2-azido-ATP, followed by separation from medium nucleotides and photolysis, a total of two sites per enzyme, both catalytic and noncatalytic, were labeled. In a coupled assay with pyruvate kinase about half the activity was lost when one site per enzyme was modified. However, increased modification resulted in no further loss of activity. In contrast, methanol-sulfite activation of the enzyme showed a loss of most of the catalytic capacity when one site per enzyme was modified. Predominant labeling of either one catalytic or one noncatalytic site caused a loss of most of the activity in either assay. An indication that the enzyme modified at one site retained some catalytic activity was verified by measurement of the [18O]Pi species formed when [gamma-18O]ATP was hydrolyzed by partially derivatized enzyme. With either catalytic or noncatalytic site modification, the distributions of [18O]Pi species formed showed that the modified enzyme had different catalytic characteristics. An interpretation is that with modification by azido nucleotides at either catalytic or noncatalytic sites, capacity for rapid catalysis is largely lost but the remaining sites retain weak modified catalytic properties.