[Analysis of 15 children with type â £ branchial cleft cyst treated with endoscopic transoral approach].

Objective: To analyze the clinical characteristics and endoscopic surgical procedures of the second branchial cleft cyst type Ⅳ in children. Methods: A retrospective review was conducted on 15 pediatric cases with type Ⅳ second branchial cleft cysts treated at the Beijing Children's Hospital affiliated with Capital Medical University and Henan Children's Hospital from September 2019 to November 2023. All patients underwent excision via a two-person, three-hand endoscopic transoral approach. The cohort included 12 males and 3 females, with an age range of 10 months to 10 years and 5 months, and a median age of (59.20±32.05) months. The clinical data of initial symptoms, sides, imaging features, treatment methods, complications, length of hospital stay, prognosis and outcome were recorded and analyzed. SPSS 22.0 software was used for statistical analysis. Results: Of the 15 children, 13 cases presented with snoring as the primary symptom, 1 case with dysphagia, and 1 case was asymptomatic and was found unintentionally. The mean disease duration was (6.74±9.05) months (range, from 3 days-2 years). MRI revealed cystic lesions on the right side in 12 cases and on the left side in 3 cases, characterized by uniform long T2 signal, equal T1 or short T1 signal. The cysts appeared dumbbell-shaped in 10 cases with the pharyngeal constrictor muscle as the waist, the posterior outside of the mass was adjacent to the internal carotid artery. The remaining 5 cases showed an isolated cyst located inside the pharyngeal constrictor muscle. The intraoperative MRI findings were consistent. Partial cystectomy was performed in 10 cases near the internal carotid artery, leaving only the portion with a clear arterial pulse intact. Five cases with isolated cysts on the medial side of the pharyngeal constrictor muscle were totally removed. The average length of hospital stay was (4.53±0.52) days (4-5 days). All patients were followed up for 7-56 months [median (30±15.12) months] with no recurrence of symptoms observed. Conclusions: The second branchial cleft cyst type Ⅳ in children is characterized by prominent pharyngeal cystic mass, with snoring as a predominant initial symptom, MRI provides excellent diagnostic value. The two-person, third-hand endoscopic transoral approach for cyst excision is feasible, safe, and offers the benefits of minimal invasiveness and reduced hospitalization time.

[Clinical characteristics and serious complications of esophageal button battery ingestion in the pediatric on 83 cases].

Objective: To analyze the clinical characteristics and complications of esophageal foreign bodies of button battery ingestion in children. Methods: A retrospective descriptive study included 83 children who were hospitalized in our hospital on account of button battery ingestion from January 2011 to December 2021. There were 50 males (60.2%) and 33 females (39.8%). The age ranged from 7.6 months to one month off 10 years, with a median age of 18 months. The data of patient demographics and time from ingestion to admission, location, symptoms, management, complications, and follow-up outcome were recorded. SPSS17.0 software was used for statistical analysis. Results: Seventy-two children (86.7%) were younger than 3 years old. The time from ingestion to admission ranged from 1 h to 2 months, with a median time of 8 h. Among the 63 children who were first diagnosed in our hospital, the most common clinical symptoms were nausea and vomiting (32 cases, 50.8%), dysphagia (31 cases, 49.2%), salivation (11 cases, 17.5%) and fever (10 cases, 15.9%). Seventy-three of 83 cases had complete preoperative diagnostic tests, and 55 cases (75.3%) were diagnosed by X-ray. In 56 cases (76.7%), the foreign badies were impacted in the upper third of esophagus. In 72 cases (86.7%), the foreign badies were removed by rigid esophagoscopy. 23 (27.7%) had serious complications, including tracheoesophageal fistula in 15 cases(TEF;65.2%), vocal cord paralysis (VCP;34.8%) in 8 cases, esophageal perforation in 3 cases (EP;13.0%), hemorrhage in 3 cases(13.0%), mediastinitis in 3 cases (13%), and periesophageal abscess in 1 case (4.3%). There were significant differences in the exposure time of foreign bodies and unwitnessed ingestion by guardians in the complications group (P<0.05). 2 cases died (2.4%)respectively due to arterial esophageal fistula bleeding and respiratory failure caused by stent displacement during the treatment of tracheoesophageal fistula. Conclusion: Accidental button battery ingestion can be life-threatening. and it mostly happens in children under 3 years old. Serious complications may happen cause of non-specific clinical manifestations and unwitnessed ingestions. Anterior and lateral chest X-ray is the first examination choice. Tracheoesophageal fistula is the most common serious complication.

[Clinical diagnosis and treatments of type â ¡-â £ congenital laryngotracheoesophageal cleft in 8 children].

Objective: To investigate the clinical diagnosis and treatment of congenital laryngotracheoesophageal cleft (LTEC) in children. Methods: The clinical data of 8 children (including 7 males and 1 female)with congenital laryngotracheoesophageal cleft from January 2016 to June 2020 were retrospectively analyzed. The median diagnosing age was 3.75 months (5 days to 12 months). According to the modified Benjamin Inglis classification proposed by Sandu in 2006,there were 3 cases of type Ⅱ, 3 cases of type Ⅲa, 1 case of type Ⅲb and 1 case of type Ⅳa. All children were followed up regularly. Results: Six patients were treated for recurrent bronchopneumonia and aspiration during feeding. The patients were first treated in the pneumology departmentt or intensive care unit. Six patients combined with other malformations. Endoscopic repair operations were performed in 6 cases (3 cases of type Ⅱ, 3 cases of type Ⅲ a), 1 case of LTEC was operated through cervical approach, and 1 case of type IVa LTEC associated with VACTERL was repaired under thoracoscope combined with suspension laryngoscope. Seven patients underwent tracheotomy before or during the repair operations. Gastrostomy was performed in 2 children. The operations were successfully performed in all cases. Three children with type Ⅱ LTEC recovered well and decannulated. One case of type Ⅲa was followed up for 5 months with occasionally choking while feeding. Two cases of type Ⅲa, 1 case of type Ⅲb and 1 case of type Ⅳa died due to severe reflux, tracheomalacia or respiratory failure. Conclusions: Congenital LTEC is a rare congenital malformation which is difficult to diagnose for the poor specificity of clinical manifestations. LTEC needs to be classified by endoscopy examination under general anesthesia. Severe cases of LTEC have poorer outcomes than the mild cases, and the perioperative managements need multi-disciplinary cooperation to reduce the mortality.

[Analysis of complications and outcomes of tracheotomy with different etiology in children].

Objective: To discuss the complications and postoperative outcomes of tracheotomy with different etiology in children. Methods: One hundred and eighty-six patients underwent tracheotomy were retrospectively analyzed from January 2016 to December 2018,including 117 males and 69 females. The children aged from 4 days to 14 years (median age 31.5months). One case was operated under local anesthesia in emergency room, 2 cases were operated under local anesthesia in pediatric intensive care unit, the rest 183 cases were operated under general anesthesia in operation room. The 186 children were divided into four groups according to their direct causes of tracheotomy. Group A(90 cases): Neuromuscular disease and severe infection,Group B(26 cases): Head and neck tumor,Group C(57 cases): Congenital malformation and upper airway obstruction,Group D(13 cases): Accidental injury. The basic information, surgical complications and postoperative outcomes were recorded and analyzed. All patients were followed up by clinic or by telephone. Spss 19.0 software was used for statistical analysis. Results: One hundred and eighty-six patients were followed up for one to four years. 33 children lost the follow-up and 46 died. Among the 186 patients, 23 cases had emergency tracheotomy (12.4%). The rate of emergency tracheotomy in group C(16 cases, 28.1%) was higher than that in the other three groups(χ2=28.08,P<0.05). The average age of patients and hospital stay in group C were significantly lower than those in the other three groups (F=33.76,P<0.05; F=14.95,P<0.05). Incision bleeding occurred in 11 cases, Subcutaneous emphysema occurred in 6 cases and accidental decannulation occurred in 10 cases (4 cases within 2 weeks and 6 after 2 weeks). Six patients underwent tracheocutaneous fistula closure operation after decannulation and the stoma healed spontaneously in other extubated children. Two patients underwent secondary tracheotomy due to accidental decannulation, and three patients underwent secondary tracheotomy for dyspnea after decannulation. In 107 cases of survival children, decannulation was successful in 65 patients and failed in 42 patients. The average duration of wearing tracheal tube was 8.8 months. The decannulation rates in the four groups were 55.6%, 45%, 69% and 77.8%, with no significant difference. Conclusions: The complications after tracheotomy in children are rare, and no severe complications occurred in long-term tracheotomy patients. The duration of wearing tracheal tube is related to the treatment of their primary disease.

[Clinical features of pulmonary thromboembolism of eight children].

Objective: To improve the diagnosis and therapy of childhood pulmonary thromboembolism (PTE) by analyzing the clinical features of this rare condition. Methods: A total of 8 pediatric patients (4 males, 4 females) with PTE diagnosed in the Children's Hospital of Zhejiang University School of Medicine from March, 2014 to March, 2019 were enrolled. The clinical manifestation, laboratory results, imaging findings, diagnosis and treatment were summarized. Results: Among these 8 cases, aged from 9 hours to 14 years and 10 months. Fever was found in 4 cases, cough aggravation in 4, short of breath in 3, chest pain in 2, abdominal and back pain in one, hemoptysis in 2, cyanosis in 1, and edema of lower extremities in 2. Physical examination found decreased breath sound in 2 cases, phlegm rale in 3, and pleural friction rub in one. Pleural effusion was found in 5 cases by ultrasound. Plasma D-dimer increased in 6 cases (0.66-9.96 mg/L) and hypersensitive C-reactive protein elevated in 5 cases (10.78-78.00 mg/L). Chest enhanced CT showed pulmonary artery or venous filling defects, including pulmonary artery embolism in 7 cases and pulmonary vein embolism in one. The primary disease of these patients included Mycoplasma Pneumoniae pneumonia in 4 cases, nephritis in 2 and postoperative congenital heart disease in 2. Apart from one case who withdrew the treatment and was discharged, the other 7 patients received anticoagulant treatment had good outcome. Conclusions: For children with Mycoplasma pneumoniae pneumonia, immune disorders, long-term hormone therapy, cardiovascular invasive operation or other high-risk factors, PTE should be considered when fever, cough aggravation, short of breath, chest and back pain with pleural effusion are present. Chest enhanced CT scan should be performed as soon as possible, and anticoagulation should be started once the diagnosis is confirmed.

Morphine alleviates myocardial ischemia/reperfusion injury in rats by inhibiting TLR4/NF-κB signaling pathway.

OBJECTIVE: The aim of this study was to investigate the effect of morphine on myocardial ischemia/reperfusion (I/R) injury in rats and its underlying mechanism, thereby providing a reference for the prevention and treatment of myocardial I/R injury in clinical practice. MATERIALS AND METHODS: A total of 60 male Sprague-Dawley (SD) rats were randomly divided into 3 groups, including: Sham group (n=20), I/R group (n=20) and I/R + morphine group (n=20) using a random number table. The left anterior descending coronary artery (LAD) of rat was ligated and re-canalized, and the I/R model was established in rats. Rats in I/R + sevoflurane (SEV) group were pretreated with 2.5% SEV. Infarction area of heart in each group was detected using triphenyltetrazolium chloride (TTC) test. Ejection fraction % (EF%) and fraction shortening % (FS%) were determined by echocardiography. Hematoxylin-eosin (HE) staining assay was performed to detect the morphological changes of cardiac myocardial cells in each group. Meanwhile, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) staining was adopted to detect the apoptosis of myocardial cells and fibroblasts. In addition, the expression levels of toll-like receptor 4 (TLR4) and p65 in heart samples of rats in each group were measured via immuno-histochemical staining. Finally, the influence of morphine on TLR4/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway was detected using Western blotting. RESULTS: Morphine significantly alleviated I/R-induced cardiac dysfunction in rats, whereas significantly increased EF% and FS% (p<0.05). In addition, morphine evidently inhibited myocardial infarction caused by I/R injury. Meanwhile, it reduced the infarction area from [(59.61±3.41) %] to [(26.67±3.62) %] (p<0.05). The results of HE staining showed that compared with I/R group, I/R + morphine group exhibited remarkably tidier cardiac myofilament, less degradation and necrosis, as well as significantly relieved cellular edema. Immuno-histochemical staining results revealed that morphine overtly reversed decreased expressions of TLR4 and p65 induced by I/R in rats (p<0.05). Furthermore, Western blotting found that morphine significantly inhibited the protein expressions of TLR4 and phosphorylated p65. CONCLUSIONS: Morphine clearly alleviates I/R-induced myocardial injury in rats. The possible mechanism may be associated with the inhibition on TLR4/NF-κB signaling pathway.

[Correlation between the visiting rate of patients with allergic rhinitis and airborne pollen concentrations in Beijing in recent 3 years].

Objective: To evaluate the daily airborne pollen concentrations and visiting rate of patients with allergic rhinitis (AR) and their correlation during 2012-2014 in Beijing. Methods: Daily airborne pollen concentrations (55 998 numbers in total and 549 numbers in average) and its constitution from April to September each year (2012 to 2014) were compared. The number of patients with AR (44 203 in total) who visited the outpatient department of Otorhinolaryngology Head and Neck Surgery, Peking University Third Hospital between January 2012 and December 2014 was analyzed by month. Using SPSS 22.0 software, Kruskal-Wallis test was done for the comparison of visiting rate of patients with AR and airborne pollen concentrations. Correlation analysis between them was made as well. Results: χ(2) value of airborne pollen concentrations between different months in 2012 to 2014 was 110.7, 108.4 and 121.4, respectively; all P<0.01. The airborne pollen concentrations had two peaks per year, respectively: April to May, August to September. χ(2) value of visiting rate of patients with AR between different months in 2012 to 2014 was 175.0, 185.1 and 134.5, respectively; all P<0.01. Visiting rate of patients with AR showed two scattering peaks each year, respectively: April to May, August to September. The highest pollen concentration of spring (April to May) was in early and middle April. Tree pollen was the major portion in spring, which were poplar pollen, pine tree pollen, ash tree pollen, cypress tree pollen and birch trees pollen. The highest pollen concentration of autumn (August to September) was in late August and early September. Weed pollen was the major portion in summer and autumn, which were artemisia pollen, chenopodiaceae pollen and humulus japonicas pollen. The visiting rate of patients with AR showed significant correlation with airborne pollen concentrations (r value was 0.537, 0.484 and 0.566, respectively; all P<0.01). Conclusion: The visiting rate of patients with AR showed positive correlation with airborne pollen concentrations in recent three years.

[The application of 3D simulationtemporal-bone-system for temporal bone anatomy training].

Objective:The aim of this study is to investigate the application of 3D simulation temporal-bone-system for temporal bone anatomy training.Method:3D simulation temporal-bone-system in the anatomy workshop was introduced in Beijing Children's Hospital from 2014 to 2015.Each participant was trained by cadaver dissection and 3D simulation temporal-bone-anatomy,and they also completed the questionnaires and evaluated the procedure.Then the difference was analyzed.Result:①In stage of mastoid outline,the damage of structure in 3D systemis higher than that in cadaver dissection(33.3%>22.2%),but there were no significant difference between them in the proportion of exposure.On the opening of attic,facial recess,facial nerve,the damage and the proportion of the non-exposed of cadaver dissection is higher.②There were no significant difference between them in the anatomical structures,levels of pollution,taste,cost and reproducibility(P>0.05),but in the aspect of time,relevance of CT with temporal bone,the similarity,and the force feedback,they had significant differences(P<0.01).Conclusion:3D simulation temporal-bone-system had better training effect in specialized otolaryngologist.It not only to help clinicians better understanding the temporal bone and surrounding structures,but also to emphasize the knowledge of the anatomy in temporal bone.

[Relationship between full flowering stages of anemophilous and ligneous plants and consultation rate of allergic rhinitis].

Objective:The aim of this study is to investigate the climatic changes on spring phenology impacting on the consultation rate of patients with allergic rhinitis.Method:We analyzed the periods of full flowering stages of 15 kinds of flowers in Beijing from 2013 to 2014,and the number of patients with allergic rhinitis in the outpatient clinic of Otolaryngology Department of Peking University Third Hospital in the same time.The correlation test, analysis of variance and rank sum test were used to investigate the inherent laws and associations between the full flowering stages and the ratio of patients with allergic rhinitis.Result:①Between 2013 and 2014,the early and middle April were the full flowering stages of Platycladus orientalis,Salix matsudana, Fraxinus chinensis,Elms and Birches.The number of patients with allergic rhinitis in outpatient clinic elevated obviously in this period.②There were overlaps of full flowering stages among different plants.During periods in which three or more kinds of pollens in full flowering stages,the consultation rate of patients with allergic rhinitis is higher than less overlaping flower period.The difference was statistically significant(F value were -2.281,-2.964 respectively, P <0.05).Also,there were obvious positive linear correlations between the number of overlap of different pollens and the consultation rate of patients with allergic rhinitis in in 2013 and 2014(r=0.957, 0.964 respectively).Conclusion:During the overlaping flower periods,there was a higher consultation rate of patients with allergic rhinitis.In prevention and treatment of allergic rhinitis,the overlapping effect of full flowering stages of different pollens should be taken into account.Upgrade the alarm level will reduce the incidence of AR and the degree of allergic rhinitis episodes.

Increasing production of matrix metalloproteinases, tumor necrosis factor-α, vascular endothelial growth factor and prostaglandin E2 in rheumatoid arthritis synovial fibroblasts by different adiponectin isoforms in a concentration-dependent manner.

Adipokines have been known to play a significant role in rheumatic disease via synovial fibroblasts. However, to date, the concentration effects of adiponectin isoforms on the pathophysiology of rheumatoid arthritis (RA) have not been extensively studied. Therefore, the present study examined the different effects of the adiponectin isoforms on rheumatoid arthritis synovial fibroblasts (RASF) and investigated the relations between the concentration of individual adiponectin isoforms and the production of the inflammatory factors of RASF. Articular synovial tissues were obtained from the patients fulfilled with diagnostic criteria of RA, and health people. RASF and human fibroblast—like synoviocytes (HFLS) were isolated and cultured. They were stimulated with increasing concentrations of 25 μg/ml, 50 μg/ml, and 100μg/ml of different human adiponectin isoforms. The levels of matrix metalloproteinase (MMP)—3, MMP—10, tumor necrosis factor (TNF)—α, vascular endothelial growth factor (VEGF), and prostaglandin E2 (PGE2) in culture supernatants were measured by immunoassays. The results showed the levels of MMP—3, MMP—10, TNF—α, VEGF and PGE2 were significantly increased in RASF which were treated with individual adiponectin isoforms compared to untreated RASF (p<0.01), and the increases also had significances compared to HFLS which were treated with the same conditions (p<0.05). Moreover, the effect of HMW (high molecular weight)/ MMW (middle molecular weight) was the strongest among them. In conclusion, all three adiponectin isoforms may contribute to proinflammatory effect by stimulating the production of MMP—3, MMP—10, TNF—α, VEGF and PGE2 of RASF in a concentration—dependent manner. HMW/MMW adiponectin could play an important role in matrix destroying and synovial vascular creating of the pathology of RA.

Pro-inflammatory cytokine-mediated ferroportin down-regulation contributes to the nigral iron accumulation in lipopolysaccharide-induced Parkinsonian models.

Pro-inflammatory cytokines induced by inflammation and iron accumulation in the substantia nigra (SN) have been implicated in the pathogenesis of Parkinson's disease (PD). In the present study, we aimed to investigate the relationship between inflammation and iron accumulation in a lipopolysaccharide (LPS)-induced Parkinsonian rat model. The activation of glial cells and elevated levels of pro-inflammatory cytokines were observed in the SN of LPS models, accompanied by iron deposits in the same region. Moreover, ferroportin (Fpn), the only channel for iron export, was down-regulated. SH-SY5Y dopaminergic cells were pre-incubated with conditioned media enriched in pro-inflammatory cytokines, and abnormal iron deposits and a drop of Fpn were observed. The expression of heme oxygenase-1 (HO-1) was also upregulated in vivo and in vitro. These results suggested that pro-inflammatory cytokines might induce Fpn downregulation, which leads to iron accumulation and dopaminergic neurons' degeneration in PD. HO-1 may also contribute to the iron accumulation in neurons, but its mechanism needs to be further investigated.

Fabrication and high visible light photocatalytic properties of Cu/Cu2O nanocomposites by the one-pot solution-phase hydrothermal method.

Cu/Cu2O nanocomposites were synthesized by the one-pot solution-phase hydrothermal method. The resulting products were characterized by X-ray diffraction, field emission scanning electron microscope and X-ray photoelectron spectroscopy. Experimental results indicate that the content of Cu in the Cu/Cu2O CNs increasing with prolonged reaction time. The content of Cu in the Cu/Cu2O CNs plays an important role in the photocatalytic activity. The coexistence of Cu2O and Cu nanoparticles was propitious to the high photocatalytic activity owing to their hetero-junction effect. Compared with the Cu/Cu2O CNs with high Cu content (68-96 wt%) and pure Cu2O, the Cu/Cu2O CNs with low Cu content (2.1-9.2 wt%) exhibited improved photocatalytic activity on the degradation of MO solution under visible light irradiation, at the first 20 min of irradiation, the photodegradation efficiency of MO solution reach up to 99%, it is still as high as 95% even at the end of the fourth cycle. Little change is found in their phase compositions during the photocatalytic reaction process, except partial oxidation of particles surface. The HmechanismH for visible light driven photocatalytic activity enhancement over Cu/Cu2O CNs is discussed.

LL-37 expression in the skin in systemic lupus erythematosus.

The objective of this study was to investigate the expression and relationship of LL-37, plasmacytoid dendritic cells (pDCs) and interferon-alpha (IFN-α) in skin in systemic lupus erythematosus (SLE), and their role in SLE pathogenesis. Skin biopsies were taken from nine SLE patients and six healthy volunteers. Expression of LL-37, pDCs and IFN-α in skin specimens and consecutive sections of skin was detected with an immunohistochemical technique (IH); the expression of LL-37 and pDCs in the samples was detected with in situ hybridization (ISH). The expression levels of LL-37, pDCs and IFN-α were significantly higher in SLE skin than in that of healthy controls (p < 0.001) with either the IH or the ISH technique, and the location of positive expression in consecutive sections was similar. Correlation analysis showed that the expression levels of LL-37, pDCs and IFN-α correlated positively with each other. In conclusion, the expression of LL-37, pDCs and IFN-α was increased in the skin of patients with active SLE. It is necessary to study further the role of LL-37 in the pathogenesis of SLE, and the exact relationship among LL-37, pDCs and IFN-α.

New laser apparatus to measure oscillation amplitude down to picometer at megahertz frequencies.

A laser setup to study shear oscillations at small amplitudes with resonance frequencies up to 3 MHz is presented. The new approach combines gauging of the Gaussian laser beam and a lock-in amplifier. The device is tested with a 3 MHz AT-cut quartz crystal. The oscillation amplitude at the edge of the electrode on the quartz crystal is measured with a resolution of 2 pm.

Impacts of ozone on the biomass and yield of rice in open-top chambers.

The impacts of different O3 concentration on the biomass and yield of rice were studied by using OTC-1 open-top chambers. Experimental treatments included the activated charcoal-filtered air (CFA), 50 nl/L (CF50), 100 nl/L (CF100) and 200 nl/L (CF200) concentrations of O3. The O3 treatments significantly decreased the total biomass per plant. The elevated O3 exposure resulted in a more decrease in the root growth than in the shoot growth. Assessments of yield characteristics at the final harvest revealed an O3-induced decrease in the number of grains per plant, resulting from fewer ears per plant, fewer grains per ear and more unfilled grains per ear. The 1000 grain dry weight and the harvest index (HI) were not changed significantly under 50 nl/L or 100 nl/L O3 exposure, but reduced by 17.0% and 4.8% by 200 nl/L O3 treatment, respectively. Compared to the CFA treatment, CF50, CF100 and CF200 treatments caused a 8.2%, 26.1%, 49.1% decrease of the grain yield per plant, and a 14.2%, 31.7%, 51.7% decrease of the total biomass per plant, respectively. Linear regression showed that the 7 h-daily mean O3 concentration exposure for 3 months (July-September) and AOT40 (cumulative exposure accumulation over threshold 40 nl/L) were well correlated with the relative grain yield. A yield loss of 10% was estimated to be at 46.9 nl/L O3 for 7 h-daily mean O3 concentration exposure or at 12930 nl/(L.h) O3 for AOT40.

Role of phosphate and kinetic characteristics of complete iron release from native pig spleen ferritin-Fe.

The kinetics for complete iron release showing biphasic behavior from pig spleen ferritin-Fe (PSFF) was measured by spectrophotometry. The native core within the PSFF shell consisted of 1682 hydroxide Fe3+ and 13 phosphate molecules. Inhibition kinetics for complete iron release was measure by differential spectrophotometry in the presence of phosphate; the process was clearly divided into two phases involving a first-order reaction at an increasing rate of 46.5 Fe3+/PSFF/min on the surface of the iron core and a zero-order reaction at a decreasing rate of 6.67 Fe3+/PSFF/min inside the core. The kinetic equation [C(PSFF-Fe3+)max - C(PSFF-Fe3+)t](1/2) = Tmax - Tt gives the transition time between the two rates and represents the complex kinetic characteristics. The rate was directly accelerated twofold by a mixed reducer of dithionite and ascorbic acid. These results suggest that the channel of the PSFF shell may carry out multiple functions for iron metabolism and storage and that the phosphate strongly affects the rate of iron release.

Studies on the heme and H2-uptake reaction from Azotobacter vinelandii bacterial ferritin.

Bacterial ferritin of Azotobacter vinelandii (AvBF) is directly able to pick electrons up for iron release from or transfer them for storage to a platinum electrode in the absence of mediator or other reducer. The ferritin containing the structure of heme-Co2+ in part shows weakened activity to electrode and decreases the rate of iron release greatly. A reversible reduction process of the ferritin is observed by the spectral change regularly ranging from 310 to 260 nm under mixed gases containing 98% H2 and 2% to O2. The activity of nitrogen fixation from the whole cell of A. vinelandii increases greatly by H2 reduction with potentials ranging from -397 to -425 mV vs. NHE, indicating two important roles of H2-uptake reaction of the ferritin in increasing activity of nitrogen fixation and in supplying iron to synthesize nitrogenase.

H2-uptake activity, spectra, reduction potentials, and kinetics of iron release on the surface of iron core from Azotobacter vinelandii bacterial ferritin.

Bacterial ferritin from Azotobacter vinelandii (AvBFo) has a function in H2 uptake. The Fe3+ reduction on the surface of the iron core from AvBFo is accompanied simultaneously by H2 uptake, with a maximum activity of H2 uptake of 450 H2/AvBFo. A reduction potential of -402 mV for iron reduction on the surface of the core is found. A shift to the red the protein absorbance peaks ranging from 280 to 290 nm is observed between pH 5 and 9 under 100% H2 reduction. The reduction potential for iron release becomes negative at a rate of 0.025 mV/Fe2+ released. The kinetics of iron release on the surface of the core is a first-order reaction.