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1.
Ann Vasc Dis ; 17(2): 150-156, 2024 Jun 25.
Article in English | MEDLINE | ID: mdl-38919324

ABSTRACT

Objectives: Distal bypass surgery's effect on tissue blood pressure beyond a focal angiosome remains debated. This study assessed tissue blood pressure in both direct revascularized angiosome (DRA) and indirect revascularized angiosome (IRA) after bypass surgery, utilizing repeated skin perfusion pressure (SPP) measurements. Methods: Twenty-nine limbs in 27 chronic limb-threatening ischemia (CLTI) patients (22 males and five females, age: 70.2 ± 9.3 years) who received distal bypass surgery were enrolled. SPP measurements were conducted for the DRA and IRA at 10 time intervals, encompassing both preoperative and postoperative periods of every 3-5 days until 30 days. Results: In total, 486 SPP measurements were collected from 58 measurement sites, and the transition of the SPP at the DRA was 35.4-62.5-59.5-70.2-58.2-62.2-63.1-63.6-63.8-73.4 mmHg and IRA was 29.4-53.4-53.7-58.8-51.3-63.1-47.9-62.1-57.6-61.0 mmHg. No significant differences were observed between SPP at the DRA and IRA. Fifteen wounds on the DRA (63%) and five on the IRA (100%) healed. Conclusion: Distal bypass improves SPP in both direct and IRAs of CLTI patients. These data indicated distal bypass improves tissue blood flow at entire foot regardless of angiosomes.

2.
J Hand Surg Asian Pac Vol ; 27(5): 928-932, 2022 Oct.
Article in English | MEDLINE | ID: mdl-36285753

ABSTRACT

Atypical ulnar fracture (AUF) is a rare condition that may occur in patients treated with bisphosphonates. We describe the clinical course of a patient who had an AUF during treatment with denosumab. An 86-year-old woman treated with denosumab for 5 years experienced a complete transverse fracture of the proximal left ulna after falling from a standing height. Intraoperative photographs showed cortical thickening around the fracture site. Therefore, we diagnosed the patient with AUF and performed internal fixation with a locking plate. However, a re-fracture occurred 2.5 months after surgery, which was treated with locking plate replacement with a longer one with a bone graft. One year after the second surgery, the fracture healed. To our knowledge, this is the second case report of an AUF occurring during denosumab treatment. Our case highlights the importance of careful follow-up of patients receiving not only bisphosphonate, but also denosumab. Levels of Evidence: Level V (Therapeutic).


Subject(s)
Bone Density Conservation Agents , Osteoporosis , Ulna Fractures , Female , Humans , Aged , Aged, 80 and over , Denosumab/adverse effects , Bone Density Conservation Agents/adverse effects , Osteoporosis/complications , Osteoporosis/drug therapy , Diphosphonates/therapeutic use , Ulna Fractures/complications , Ulna Fractures/diagnostic imaging , Ulna Fractures/surgery
3.
JBJS Case Connect ; 12(2)2022 04 01.
Article in English | MEDLINE | ID: mdl-35696716

ABSTRACT

CASE: A 77-year-old woman with bilateral symptomatic atypical femoral fractures (AFFs) and severe anterolateral bowing due to long-term bisphosphonate administration was treated using stainless elastic intramedullary nails. Weight-bearing pain disappeared immediately after surgery. Radiographs obtained 1 year postoperatively showed fracture healing. CONCLUSION: Although intramedullary nail insertion has been recommended for symptomatic incomplete AFFs, in cases of severe bowing, rigid nail insertion was often challenging, and the complication rates were higher than those with mild bowing. The advantage of our method is easy insertion, suggesting effective treatment.


Subject(s)
Femoral Fractures , Fracture Fixation, Intramedullary , Aged , Bone Nails , Female , Femoral Fractures/diagnostic imaging , Femoral Fractures/surgery , Femur , Fracture Healing , Humans
5.
J Cachexia Sarcopenia Muscle ; 13(2): 945-954, 2022 04.
Article in English | MEDLINE | ID: mdl-35170256

ABSTRACT

BACKGROUND: The sarcopenia index (SI), calculated as the ratio of serum creatinine to cystatin C levels, reflects skeletal muscle mass and strength. Patients with hip fracture (HF) and sarcopenia have poor functional outcomes, and many require long-term care after surgery. We hypothesized that the SI can predict preoperative and early postoperative functional outcomes. METHODS: Preoperative serum creatinine and cystatin C were measured to calculate the SI for patients with surgically treated HF (n = 130, mean age: 87.8 ± 6.9 years). Walking ability before and 2 weeks after surgery was assessed, and patients were dichotomized into independent and assistance groups. To assess the validity of the SI, we examined its correlation with the quality [computed tomography (CT) value] and quantity (cross-sectional area) of the muscles around the hip on the non-operated side, which were preoperatively measured using CT. Receiver operating characteristic (ROC) analysis was performed to evaluate the prognostic value of the SI. RESULTS: The SI of the preoperative independent (n = 77) and assistance groups (n = 53) significantly differed (70.2 ± 12.4 and 60.1 ± 9.8, respectively, P < 0.000001). At 2 weeks after surgery, the SI was significantly higher in the independent group (n = 31, 73.0 ± 14.9) than in the assistance group (n = 99, 64.0 ± 10.7, P = 0.0003). In the preoperative independent group, 28 could walk independently after surgery (SI: 74.8 ± 14.0) while 49 required assistance (SI: 67.7 ± 10.6, P = 0.01). For patients with femoral neck fracture (FNF), the SIs were significantly higher in the postoperative independent group (78.6 ± 15.7) than in the postoperative assistance group (63.2 ± 10.9, P = 0.002). Logistic regression analysis showed that the odds ratio (95% confidence interval) of the SI for postoperative walking ability was 0.95 (0.91-0.99, P = 0.03). The correlations of SIs with CT values and cross-sectional areas were as follows: iliopsoas at the apex of the femoral head, r = 0.40, P < 0.001 and r = 0.49, P < 0.001, respectively; rectus femoris at the level of the lessor trochanter, r = 0.26, P = 0.007 and r = 0.37, P < 0.001, respectively. ROC analysis for predicting postoperative walking ability in preoperative independent patients with HF and FNF revealed areas under the curve (95% confidence interval) of 0.63 (0.50-0.76) and 0.80 (0.65-0.96), respectively. CONCLUSIONS: In patients with HF, the SI correlated with preoperative walking ability and could predict postoperative walking ability. Among patients who could walk independently before surgery, those with high SIs could walk independently early in the postoperative period. The SI is beneficial for estimating walking ability in patients with HF.


Subject(s)
Cystatin C , Sarcopenia , Aged , Aged, 80 and over , Creatinine , Humans , Postoperative Period , Sarcopenia/diagnosis , Walking
6.
Eur J Vasc Endovasc Surg ; 62(2): 187-192, 2021 08.
Article in English | MEDLINE | ID: mdl-33608205

ABSTRACT

OBJECTIVE: Open repair surgery (ORS) for an abdominal aortic aneurysm (AAA) remains an important treatment option, but the incidence of para-anastomotic aneurysms is unclear. The purpose of this study was to estimate the incidence of para-anastomotic aneurysms and reveal secondary complications through routine annual computed tomography (CT) imaging. METHODS: One hundred and forty-seven patients who underwent ORS for AAA between January 2006 and December 2015 and received routine CT imaging surveillance were enrolled. RESULTS: The follow up period was 7.1 ± 2.7 years. The total follow up time of all patients was 1 041.1 years, and 958 CT images were collected (0.92 CT scans/year/patient). A proximal para-anastomotic aneurysm was detected in five patients (3.4%). Four of the five patients had aneurysmal dilation at the initial ORS (proximal diameter >25 mm), which enlarged during follow up; thus, a de novo proximal para-anastomotic aneurysm was observed in one patient (0.7%). The time between surgery and the diagnosis of all proximal para-anastomotic aneurysms was 5.7 ± 1.4 years, and the de novo proximal para-anastomotic aneurysm was detected at 11.8 years. The incidence of all para-anastomotic aneurysms at five and 10 years was 2.2% and 3.6%, and the incidence of the de novo para-anastomotic aneurysm was 0% at five and 10 years. Nine synchronous thoracic aortic aneurysms (TAAs) and seven metachronous TAAs were detected, and 16 patients (10.9%) had a TAA. Neoplasms were detected in 18 of 147 patients (12.2%), and the most dominant neoplasm was lung cancer. CONCLUSION: The incidence of para-anastomotic aneurysms was low; thus, abdominal and pelvic CT imaging every five years may be sufficient and consistent with the current AAA guidelines. In contrast, TAAs were diagnosed in a high percentage of patients, and based on these observations, routine CT imaging should be expanded to include the chest.


Subject(s)
Aorta, Abdominal/surgery , Aortic Aneurysm, Abdominal/epidemiology , Aortic Aneurysm, Abdominal/surgery , Aortic Aneurysm, Thoracic/epidemiology , Lung Neoplasms/epidemiology , Aged , Anastomosis, Surgical , Aortic Aneurysm, Abdominal/diagnostic imaging , Aortic Aneurysm, Thoracic/diagnostic imaging , Comorbidity , Female , Follow-Up Studies , Humans , Incidence , Japan/epidemiology , Lung Neoplasms/diagnostic imaging , Male , Middle Aged , Proportional Hazards Models , Retrospective Studies , Risk Factors , Tomography, X-Ray Computed
7.
Ann Vasc Dis ; 13(4): 447-449, 2020 Dec 25.
Article in English | MEDLINE | ID: mdl-33391569

ABSTRACT

We present a case of superior mesenteric venous thrombosis (SMVT) treated successfully with thrombectomy without bowel resection. A 73-year-old female was referred to our hospital with complaints of stomach ache. The patient was diagnosed with SMVT with impending bowel necrosis and underwent an emergency operation, after computed tomography (CT) revealed a thrombus in the superior mesenteric vein (SMV) extending to the splenic vein, ascites, and extremely edematous intestines. The intestines were not necrotic though highly congested. To avoid massive bowel resection, aggressive thrombectomy was performed. Postoperative CT confirmed resolved SMV and improved bowel edema. Prompt thrombectomy should be considered in such cases.

8.
J Hand Surg Eur Vol ; 45(2): 187-192, 2020 Feb.
Article in English | MEDLINE | ID: mdl-31722639

ABSTRACT

The most common thumb deformity in rheumatoid arthritis is Nalebuff Type 1 deformity (boutonniere deformity). Type 1 deformity severely impairs hand function, and this impairment is evaluated by the Terrono classification. In some cases, the Terrono classification incorrectly categorizes advanced thumb deformity into earlier stages. We modified the Terrono classification by assessing the active range of motion of the interphalangeal joint prior to assessing the passive range of movement of the metacarpophalangeal joint. An active range of movement of the interphalangeal joint was strongly correlated with hand function. In 55 hands that we treated between 2004 and 2015, we compared the modified classification with the original Terrono classification. Our modified classification could detect advanced deformity earlier, and was more strongly correlated with hand function. Additionally, correlation analysis showed that advanced Type 1 deformity should be treated first, even in cases with severe ulnar drift. Our results suggest that the modified classification may benefit the treatment of Type 1 deformity, including joint-preserving surgery. Level of evidence: III.


Subject(s)
Arthritis, Rheumatoid , Hand Deformities, Acquired , Arthritis, Rheumatoid/complications , Cross-Sectional Studies , Hand Deformities , Hand Deformities, Acquired/etiology , Hand Deformities, Acquired/surgery , Humans , Metacarpophalangeal Joint/surgery , Thumb/abnormalities , Thumb/surgery
9.
Biomed Mater Eng ; 30(5-6): 475-486, 2020.
Article in English | MEDLINE | ID: mdl-31771032

ABSTRACT

BACKGROUND: We have developed a technology to electrically polarize living bone. OBJECTIVE: The effects of stored electrical charge in electrical polarized bone on the facilitation of new bone formation were assayed. METHODS: Stimulated depolarized current measurement was performed in electrically polarized and nonpolarized femora of SD rats. These bone specimens were implanted into bone defects of the rat femora and fixed with a custom-made external fixator. X-ray imaging of the implant was performed every week. After 3 weeks, micro-CT scanning was performed to evaluate the displacement rate. Histological observation was performed, and the occupancy ratio of the newly formed bone was calculated from tissue specimens stained with Villanueva's Goldner method. RESULTS: There was a tendency for the displacement rate of the implant to be smaller and the occupancy ratio of the newly formed bone to be larger, especially at the distal end, in the polarized group compared with the nonpolarized group. The time of callus appearance was significantly earlier in the polarized group than in the nonpolarized group, and bridging callus grew from the distal to the proximal end. CONCLUSIONS: Bone specimens can be electrically polarized, and the stored electrical charge can work effectively to facilitate new bone formation.


Subject(s)
Electric Stimulation Therapy , External Fixators , Femoral Fractures/therapy , Implants, Experimental , Animals , Body Temperature/physiology , Bone Regeneration/physiology , Disease Models, Animal , Electric Stimulation , Electric Stimulation Therapy/instrumentation , Electric Stimulation Therapy/methods , Electricity , Femoral Fractures/pathology , Male , Osteogenesis/physiology , Precision Medicine/instrumentation , Rats , Rats, Sprague-Dawley , Treatment Outcome
10.
Ann Vasc Dis ; 12(3): 347-353, 2019 Sep 25.
Article in English | MEDLINE | ID: mdl-31636745

ABSTRACT

Objective: To examine the medium- to long-term outcomes of acute limb ischemia (ALI), which are unclear at present. Methods: We analyzed 93 consecutive limbs in 77 patients with ALI between January 2005 and December 2015 treated at our vascular center. We categorized the cases into four groups according to etiology (embolism, thrombosis, graft thrombosis, and dissection groups) to assess survival, limb salvage, and freedom from re-intervention rates. Results: The mean age at onset was 72±15 years. The median follow-up length was 2.90 years. The Rutherford categories I, IIa, IIb, and III included 1, 38, 51, and 3 cases, respectively. Thromboembolectomy was performed in all patients in the embolism and thrombosis groups. In addition, endovascular treatment was performed in 25 (37.3%) patients, especially in the thrombosis group (81.3%). A major amputation could not be avoided in 10 patients. The 5-year limb salvage rates for categories IIa and IIb were 97.1% and 83.1%, respectively. The 5-year freedom from re-intervention rate was 89.2%. The survival rates at 1, 3, and 5 years were 87.9%, 75.2%, and 60.6%, respectively. Conclusion: The 5-year survival rates of patients with ALI were equivalent to those with chronic limb threatening ischemia (CLTI). The intervention and long-term outcomes were distinguishable according to etiology.

11.
Tohoku J Exp Med ; 249(2): 113-119, 2019 10.
Article in English | MEDLINE | ID: mdl-31656241

ABSTRACT

Clinical application of accumulated medical big data is a hot topic in medical informatics. Not only for suggesting possible diagnoses in each individual, large medical database can be possibly used for detecting undiagnosed patients in the general population. In this study, we tried to develop a computerized system of detecting overlooked undiagnosed patients with rare chronic diseases in the community population by utilizing the uniformed national medical insurance record database. A cumulative total of 489,823 hospital visits at one tertiary medical center were collected for this project. As the target disease, we selected esophagogastric junction outflow obstruction (EGJOO), including achalasia, which is known to be easily overlooked without performing a barium swallow test. Patient selection software automatically picked out 17,814 individuals with the given suspected diagnoses that could be misdiagnosed in patients with the target disease, from which the software further picked out 526 individuals who underwent upper endoscopy but did not undergo barium swallow test. Of them, the hospital medical records suggested that 39 people still suffered from prolonged symptoms lasting for more than 6 months after the first hospital visit. Among them, 16 individuals agreed to undergo the barium swallow test. One of them was confirmed to suffer from EGJOO, possibly based on some undiagnosed connective tissue diseases. An automated computerized detection system with uniform big medical data would realize more efficient and less expensive screening system for undiagnosed chronic diseases in the general population based on symptoms and previously performed examinations in each individual.


Subject(s)
Databases as Topic , Electronic Health Records , Adolescent , Adult , Artificial Intelligence , Child , Esophagogastric Junction/pathology , Female , Fluoroscopy , Humans , Male , Middle Aged , Young Adult
12.
Ann Vasc Surg ; 56: 29-35, 2019 Apr.
Article in English | MEDLINE | ID: mdl-30500644

ABSTRACT

BACKGROUND: Patients presenting with edema, skin redness, pain, and itching in their lower legs are common and encountered often in daily practice. However, although commonly recognized diseases such as deep venous thrombosis, stasis dermatitis due to varicose veins, lymphedema, and cellulitis are diagnosed correctly in most cases, micro-arteriovenous fistulas (AVFs) may often be overlooked due to low awareness and rarity. This study was carried out to evaluate the prevalence of micro-AVF in patients presenting with foot skin symptoms. METHODS: A total of 134 patients (184 limbs) visited the Department of Vascular Surgery at Kesennuma City Hospital with edema, skin redness, pain, and itching in their lower legs from January to September 2017 and were enrolled and followed up until November 2017. All patients received ultrasonic inspection of their symptomatic limb, and a blood test (white blood cell count, C-reactive protein, and d-dimer) was performed if needed. When micro-AVF was detected in one limb, the other limb was routinely inspected by ultrasonography. A computed tomography scan was performed with the patient's consent. Patients diagnosed with micro-AVF started compression therapy immediately and were followed up for at least 2 months. A surgical procedure was considered if the symptoms worsened. RESULTS: Micro-AVFs were detected in 24 limbs (13%, 24/184) of 14 patients (7 males and 7 females; age 70 ± 11.7 years). Four patients had unilateral skin symptoms with unilateral micro-AVFs and 7 patients had unilateral skin symptoms and bilateral micro-AVFs. Three patients had bilateral skin symptoms and bilateral micro-AVFs. Asymptomatic micro-AVFs were detected in 7 limbs. Subjective symptoms disappeared and skin appearance normalized in 14 limbs of 12 patients during the first 2 months with compression therapy only. Compression therapy was not effective in 3 limbs of 2 patients and they underwent vein ligation surgery. None of the patients had a surgical history or history of trauma in their lower legs. CONCLUSIONS: Among the lower legs presenting with skin symptoms, we detected micro-AVFs in 13% of limbs; therefore, micro-AVF of the lower leg is not as rare as previously thought. In addition, 10 of 14 patients (71%) had micro-AVFs of the lower leg bilaterally.


Subject(s)
Arteriovenous Fistula/epidemiology , Lower Extremity/blood supply , Adult , Aged , Aged, 80 and over , Arteriovenous Fistula/diagnostic imaging , Arteriovenous Fistula/physiopathology , Arteriovenous Fistula/therapy , Computed Tomography Angiography , Edema/epidemiology , Erythema/epidemiology , Female , Humans , Incidence , Japan/epidemiology , Male , Microcirculation , Middle Aged , Pain/epidemiology , Prevalence , Prognosis , Pruritus/epidemiology , Regional Blood Flow , Retrospective Studies , Time Factors , Ultrasonography
13.
Int J Surg Case Rep ; 48: 87-91, 2018.
Article in English | MEDLINE | ID: mdl-29913431

ABSTRACT

INTRODUCTION: Closed flexor tendon rupture after a malunited distal radius fracture is rare and usually becomes apparent early after the fracture. Most cases are accompanied by a severe distal radio-ulnar joint capsule injury, wherein bone protrusion (as a spur) directly stresses the tendons. We experienced a nonspecific flexor tendon rupture associated with an old fracture and the presence of collagen disease. PRESENTATION OF CASE: A 63-year-old woman presented with delayed complete rupture of the flexor digitorum profundus (FDP) of the fifth digit. Her history included closed fracture on the left wrist at age 13 years. At 27 years, she was diagnosed with Behçet syndrome and commenced oral prednisolone 10 mg/day. At the current admission, physical examination revealed that she was incapable of fifth finger flexion after minor passive extension. The fifth digit FDP rupture appeared to be due to damage at the wrist-level fracture site. A tiny capsule rupture was seen on the volar side of the distal radio-ulnar joint. We resected ulnar head osteophytes protruding from the capsule hole and transferred tendon from the fifth FDP to the fourth FDP. CONCLUSION: Reportedly, metalloproteases weaken tendon structure by acting as a collagenase in patients with Behçet syndrome. Also, vasculitis next to a tendon and steroid intake are considered to impede the tendon repair process. Hence, even minor trauma may lead to complete tendon rupture. Although an injury seems slight, we should take into account the possible history of bone and joint trauma.

14.
Circ J ; 81(12): 1774-1782, 2017 Nov 24.
Article in English | MEDLINE | ID: mdl-28674268

ABSTRACT

BACKGROUND: The maximum axial diameter (MAD) of a fusiform abdominal aortic aneurysm (AAA) is an indicator of the risk of expansion or rupture. Apart from smoking and MAD itself, few expansion risk factors have been reported. In this study, we investigated expansion risk factors for AAA.Methods and Results:This retrospective cohort study included 176 patients who attended Tohoku University Hospital with infrarenal fusiform AAA. AAA expansion rate was determined on multidetector computed tomography, and the correlations between expansion rate and the clinical data were analyzed. The median expansion rate was 2.405 mm/year. On univariate analysis, a significant positive correlation with expansion rate was observed for the initial MAD (P<0.001) and significant negative correlations for oral angiotensin receptor blocker usage (P=0.025), height (P=0.005), body weight (P=0.017), total cholesterol (P=0.007), low-density lipoprotein cholesterol (P=0.004), and HbA1c (P=0.037). On logistic regression analysis, significant positive associations with expansion rate were observed for initial MAD (P<0.001) and oral steroid usage (P=0.029) and a negative association for height (P=0.041). CONCLUSIONS: Oral steroid usage is an important risk factor for AAA expansion, independent of other risk factors of atherosclerosis and MAD.


Subject(s)
Aortic Aneurysm, Abdominal/pathology , Aged , Aortic Aneurysm, Abdominal/diagnosis , Aortic Rupture , Body Height , Disease Progression , Humans , Multidetector Computed Tomography , Retrospective Studies , Risk Factors , Steroids/adverse effects , Steroids/therapeutic use
15.
Ann Vasc Dis ; 10(4): 411-416, 2017 Dec 25.
Article in English | MEDLINE | ID: mdl-29515705

ABSTRACT

Objective: Renal artery aneurysm (RAA) is an uncommon disease, the natural course of which is still not well known. The objective of this study is to define factors that affect the growth rate of RAAs. Materials and Methods: We retrospectively reviewed 32 aneurysms in 26 patients at our institute between January 2010 and March 2016. Basal demographics, comorbidities, reason for diagnosis, and details of the aneurysms and interventions were recorded. The chronological changes in the diameter of the RAA using multiplanar reconstructions of computed tomography images were measured and analyzed. Results: The baseline mean diameter was 20.1±8.4 mm (range: 9.9-41). The mean follow-up period was 3.13±2.1 y (range: 0.5-7.1). The median growth rate was 0.35 mm/y (interquartile range: 0.05, 0.62). The growth rate was slower when the initial diameter was <20 mm than when it was >20 mm (p=0.036). Also, whole-completed calcification was a significant factor for slower growth (p=0.016). We performed ex-vivo surgery in two cases and coil packing with stenting in one. No ruptures occurred during the study period. Conclusion: Our results suggest that cases with an RAA diameter <20 mm do not require intervention. The interval period can be longer in whole-completed calcification types.

16.
Gan To Kagaku Ryoho ; 36(7): 1171-4, 2009 Jul.
Article in Japanese | MEDLINE | ID: mdl-19620811

ABSTRACT

A 75-year-old man was diagnosed with gastric cancer (UL post c0- II c (c T1N0) and M-less ctype II (cT2N0)) and rectal cancer (Rb ctype II (cT2N1) with multiple lung metastases (M1). The patient was treated with modified (m) FOLFOX6 regimen (oxaliplatin in combination with infusional 5-fluorouracil/Leucovorin). Chest and abdominal CT scan revealed that multiple lung metastases and abdominal lymph node metastases were obviously reduced in size. The primary lesion of the rectum almost disappeared on endoscopic examination. As for the lesions of the stomach, the UL post c0- II c lesion completely disappeared, and the M-less ctype II lesion was reduced remarkably. Thus, a significant reduction of the tumors was observed. This case suggests that mFOLFOX6 regimen can be an option for gastric cancer.


Subject(s)
Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Neoplasms, Multiple Primary/drug therapy , Rectal Neoplasms/drug therapy , Stomach Neoplasms/drug therapy , Aged , Antimetabolites, Antineoplastic/administration & dosage , Antineoplastic Agents/administration & dosage , Fluorouracil/administration & dosage , Humans , Leucovorin/administration & dosage , Male , Organoplatinum Compounds/administration & dosage , Oxaliplatin , Vitamin B Complex/administration & dosage
17.
Acta Crystallogr D Biol Crystallogr ; 63(Pt 2): 221-9, 2007 Feb.
Article in English | MEDLINE | ID: mdl-17242515

ABSTRACT

Intracellular nickel is required by Escherichia coli as a cofactor for a number of enzymes and is necessary for anaerobic respiration. However, high concentrations of nickel are toxic, so both import and export systems have evolved to control the cellular level of the metal. The nik operon in E. coli encodes a nickel-uptake system that includes the periplasmic nickel-binding protein NikA. The crystal structures of wild-type NikA both bound to nickel and in the apo form have been solved previously. The liganded structure appeared to show an unusual interaction between the nickel and the protein in which no direct bonds are formed. The highly unusual nickel coordination suggested by the crystal structure contrasted strongly with earlier X-ray spectroscopic studies. The known nickel-binding site has been probed by extensive mutagenesis and isothermal titration calorimetry and it has been found that even large numbers of disruptive mutations appear to have little effect on the nickel affinity. The crystal structure of a binding-site mutant with nickel bound has been solved and it is found that nickel is bound to two histidine residues at a position distant from the previously characterized binding site. This novel site immediately resolves the conflict between the crystal structures and other biophysical analyses. The physiological relevance of the two binding sites is discussed.


Subject(s)
ATP-Binding Cassette Transporters/chemistry , Binding Sites , Escherichia coli Proteins/chemistry , Nickel/chemistry , ATP-Binding Cassette Transporters/metabolism , Calorimetry , Crystallography , Escherichia coli Proteins/metabolism , Nickel/metabolism , Protein Conformation , Spectrum Analysis
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