Personality and Sleep Evaluation of Patients with Tinnitus in Japan.

In Japan, there have been no examinations of tinnitus with respect to personality traits, and only a few studies have investigated sleep disorders in tinnitus. Understanding the association between these can aid in selecting and developing effective treatment options for patients with tinnitus. This study aimed to clarify the relationship between tinnitus severity, personality, and sleep disorders, in patients with chronic tinnitus in Japan. We retrospectively evaluated the personality factors of 56 patients presenting with tinnitus using the NEO Five-Factor Inventory (NEO-FFI), which examines five personality characteristics, including Neuroticism, Extraversion, Openness, Agreeableness, and Conscientiousness. We evaluated tinnitus severity, sleep disorders, depression, and anxiety using the Tinnitus Handicap Inventory, Pittsburgh Sleep Quality Index (PSQI), Self-Rating Depression Scale, and State-Trait Anxiety Inventory, respectively. Neuroticism and tinnitus severity were positively correlated (r = 0.548, p < 0.001). Sleep disorders were observed in 73.2% of patients; however, there was no correlation between the PSQI score and tinnitus severity or between PSQI score and scores of the five NEO-FFI items. Sleep disorders are frequently experienced by patients with chronic tinnitus, regardless of tinnitus severity or personality. Understanding the relationship between personality and tinnitus severity could lead to better management of tinnitus.

Development of an Oropharyngeal Scope with an Integrated Tongue Depressor: NTOP2013 Study.

The oropharynx is examined with a light source such as an electric light, a penlight, or a forehead mirror based on an acquired visual field using a tongue depressor. However, it is extremely difficult to obtain objective and reproducible images of tissue within the pharynx required in recent years with these methods, and insufficient progress in the examination tools has been made. There is an increasing need to develop a method for display during oropharyngeal examination. We conducted the present study to develop a novel oropharyngeal endoscope as an objective observation method.

Analysis of vestibular-balance symptoms according to symptom duration: dimensionality of the Vertigo Symptom Scale-short form.

BACKGROUND: Dizziness or vertigo is associated with both vestibular-balance and psychological factors. A common assessment tool is the Vertigo Symptom Scale (VSS) -short form, which has two subscales: vestibular-balance and autonomic-anxiety. Despite frequent use, the factor structure of the VSS-short form has yet to be confirmed. Here, we clarified the factor structure of the VSS-short form, and assessed the validity and reliability of the Japanese version of this tool. METHODS: We conducted a cross-sectional, multicenter, psychometric evaluation of patients with non-central dizziness or vertigo persisting for longer than 1 month. Participants completed the VSS-short form, the Dizziness Handicap Inventory, and the Hospital Anxiety and Depression Scale. They also completed the VSS-short form a second time 1-3 days later. The questionnaire was translated into Japanese and cross-culturally adapted. We conducted a confirmatory factor analysis followed by an exploratory factor analysis. Convergent and discriminant validity, internal consistency, and test-retest reliability were evaluated. RESULTS: The total sample and retest sample consisted of 159 and 79 participants, respectively. Model-fitting for a two-subscale structure in a confirmatory factor analysis was poor. An exploratory factor analysis produced a three-factor structure: long-duration vestibular-balance symptoms, short-duration vestibular-balance symptoms, and autonomic-anxiety symptoms. Regarding convergent and discriminant validity, all hypotheses were clearly supported. We obtained high Cronbach's α coefficients for the total score and subscales, ranging from 0.758 to 0.866. Total score and subscale interclass correlation coefficients for test-retest reliability were acceptable, ranging from 0.867 to 0.897. CONCLUSIONS: The VSS-short form has a three-factor structure that was cross-culturally well-matched with previous data from the VSS-long version. Thus, it was suggested that vestibular-balance symptoms can be analyzed separately according to symptom duration, which may reflect pathophysiological factors. The VSS-short form can be used to evaluate vestibular-balance symptoms and autonomic-anxiety symptoms, as well as the duration of vestibular-balance symptoms. Further research using the VSS-short form should be required in other languages and populations.

[A Retrospective Series of 77 Pediatric Patients with Vertigo at a National Center for Child Health and Development].

The evaluation and management of vertigo in children varies among institutional and medical specialties. The aim of this study was to describe the characteristics of vertigo in children presenting at a national pediatric center. Patients < 16 years old presenting with vertigo to the department of otolaryngology at a national center for child health and development from April 2004 to October 2009 were included (N = 77; 42 males and 35 females; average age, 8.7 ± 3.4 years) in this study. The most common diagnoses were vestibular migraine (VM; N = 21), benign paroxysmal vertigo (BPV; N =16), unilateral vestibulopathy (N = 12), and psychogenic vertigo (N = 8). Significant differences were observed in the frequency of the diagnoses between children aged older and younger than 7 years: BPV was most common in children < 7 years of age (p < 0.01) and VM was most common in ≥ 27 years of age (p < 0.05). Because obtaining adequate information from children for making a correct diagnosis is sometimes difficult, acquiring sufficient information from the parents is important. In addition, getting the parents to record the nystagmus during a vertigo attack with a digital camera or cellular phone can be useful because observing the nystagmus recorded on the video is helpful for making a diagnosis. Furthermore, the parents are participating in their child's care by attempting to record the attack, strengthening the relationship between the parents and the child. The incidence of psychogenic vertigo is low (less than 10%). Therefore, although physicians have recently tended to define the disorder as psychogenic when no objective abnormality is found in a patient, making a diagnosis of psychogenic vertigo is not recommended. Because vertigo can sometimes make a child anxious, delivering the correct diagnosis and treatment at the early stage is important for preventing anxiety in affected children.

A kinetic analysis of cadmium accumulation in a Cd hyper-accumulator fern, Athyrium yokoscense and tobacco plants.

Cadmium (Cd) accumulations in a Cd hyper-accumulator fern, Athyrium yokoscense (Ay), and tobacco, Nicotiana tabacum (Nt), were kinetically analysed using the positron-emitting tracer imaging system under two medium conditions (basal and no-nutrient). In Ay, maximumly 50% and 15% of the total Cd accumulated in the distal roots and the shoots under the basal condition, respectively. Interestingly, a portion of the Cd in the distal roots returned to the medium. In comparison with Ay, a little fewer Cd accumulations in the distal roots and clearly higher Cd migration to the shoots were observed in Nt under the basal condition (maximumly 40% and 70% of the total Cd, respectively). The no-nutrient condition down-regulated the Cd migration in both species, although the regulation was highly stricter in Ay than in Nt (almost no migration in Ay and around 20% migration in Nt). In addition, the present work enabled to estimate physical and physiological Cd accumulation capacities in the distal roots, and demonstrated condition-dependent changes especially in Ay. These results clearly suggested occurrences of species-/condition-specific regulations in each observed parts. It is probable that integration of these properties govern the specific Cd tolerance/accumulation in Ay and Nt.

Habituation disorders in auditory middle latency response of persistent postural-perceptual dizziness patients.

Objectives: To study habituation disorders in auditory middle latency response (AMLR) to repetitive stimuli of persistent postural-perceptual dizziness (PPPD) patients. Subjects: Twenty-eight PPPD (10 men and 18 women, mean 59.5 years of age, 26-81 years of age) were enrolled. For comparison, data of 13 definite vestibular migraine (VM) patients (3 men, 10 women, mean age 45.5), 13 definite unilateral Meniere's disease (MD) patients (2 men, 11 women, mean age 50.6), and 8 healthy control (HC) subjects (2 men, 6 women, mean age 37.1) in the previous study were utilized. Methods: The electrodes were placed on the vertex and the spinal process of the fifth cervical vertebra. Clicks (0.1 msec, 70 dB nHL) were binaurally presented and averaged (800 times). Averaged responses were divided into 4 sets (S1 to S4) according to the temporal order. As peaks, Na, and Pa were identified, and relative Na-Pa amplitudes in S2-S4 to S1 were analyzed. Results: The mean relative amplitude of PPPD patients showed lack of habituation (potentiation) as shown in VM patients, although the extent of potentiation was weaker than VM. Comparison of relative S4 amplitudes showed significant differences among the 4 groups (p = 0.0013 one-way ANOVA), Multiple comparison revealed significant differences between PPPD and MD (p = 0.0337 Dunnet's test). Conclusion: PPPD patients showed lack of habituation (potentiation) of Na-Pa amplitude in AMLR to repetitive stimuli. Lack of habituation (potentiation) might be associated with sensory processing disorders in PPPD.

Prognostic significance vestibular examination results in patients with vestibular migraine.

Introduction: Vestibular migraine (VM) is a newly defined clinical condition. Several vestibular abnormalities have been reported in patients with VM. However, to date, no specific vestibular examinations are used to define VM. Therefore, the utility of vestibular examinations is limited. Currently, the role of vestibular examination has not been clearly defined. We speculated that the results of vestibular examinations could predict the prognosis of VM. We investigated the relationship between the vestibular examination results and clinical outcomes in patients with VM. Methods: This study included 25 patients with VM. Vestibular examinations, including the video head impulse test (V-HIT), cervical and ocular vestibular evoked myogenic potential (c-VEMP and o-VEMP), posturography, and several questionnaires, including the Dizziness Handicap Inventory (DHI), were conducted at the initial evaluation. Lifestyle modifications for VM and conventional pharmacological prophylactic treatments, including lomerizine, amitriptyline, and valproic acid, were performed. After 4 weeks of treatment, clinical improvements were evaluated using the Clinical Global Improvement Scale (CGI-s). The relationships among the CGI-S score, several clinical variables, and the results of several vestibular examinations were evaluated. Each patient was further classified into two subgroups according to treatment outcomes concerning vertigo and headache: CGI-S score from 0 to 2 (good response [GR]) and CGI-S score > 3 (poor response [PR]). Results: Overall, after treatment, most of the patients had improved dizziness and headache, and the CGI-s was 2.7 ± 1.3. There were 12 GRs, and 13 had PRs. Thus, neither V-HIT nor posturography predicted the prognosis. For c-VEMP, patients with GRs had significantly small AR concerning PR (19.2 ± 12.8 and 62.5 ± 42.5, respectively, [p < 0.01]). There were five normal, six unilateral, and 14 bilateral no response in 500hz o-VEMP. CGI-s of normal, unilateral, and bilateral no response was 1.4 ± 0.5, 2.8 ± 1.3, and 3.1 ± 1.2, respectively. There was a statistically significant difference between the normal and bilateral non-response o-VEMP groups (p < 0.05). Conclusion: Patients with VM had improvements in both headache and vertigo through a combination of lifestyle changes and prophylactic medications. Vestibular examinations, especially o- or c-VEMP, are beneficial for predicting the treatment outcomes of VM. The pathophysiology of VM is closely related to vestibular abnormalities, particularly the otolith-related pathways.

Allergic Fungal Rhinosinusitis and Contralateral Chronic Granulomatous Invasive Fungal Sinusitis: A Case Report.

This case report describes rare concomitant allergic fungal rhinosinusitis (AFRS) and chronic granulomatous invasive fungal sinusitis (CGIFS) in a 34-year-old woman with acute lymphoblastic leukemia and graft-versus-host disease (GVHD) post bone marrow transplantation. Initially presenting with rhinorrhea and nasal obstruction, the patient was diagnosed with AFRS in the right maxillary sinus, followed by a postoperative course of CGIFS in the left nasal cavity, showcasing the unique occurrence. She was not immunocompromised during diagnosis. CGIFS may have occurred because of surgery; however, voriconazole led to significant improvement. This case highlights noninvasive and invasive fungal infections in patients with chronic rhinosinusitis and a history of GVHD and underscores the complexity of diagnosing and managing such cases.

Swallowing Function and Quality of Life in Patients Treated With Transoral Videolaryngoscopic Surgery for Pharyngolaryngeal Cancer.

BACKGROUND: It is controversial whether transoral resection for early pharyngolaryngeal cancer preserves swallowing function and quality of life. We investigated swallowing function and quality of life before and after transoral videolaryngoscopic surgery (TOVS). METHODS: Seventy-three patients with pharyngolaryngeal cancer who underwent TOVS between July 2012 and July 2022 were enrolled in this prospective analysis. The Hyodo score and European Organization for Research and Treatment of Cancer Quality of Life Questionnaires were recorded preoperatively and at three, six, and 12 months postoperatively, in addition to the postoperative functional outcome swallowing scale (FOSS) at six months postoperatively. RESULTS: Although most patients could consume food orally without restrictions with a preferable FOSS score, 23 patients showed impaired Hyodo scores. Age ≥65 years significantly predicted impaired swallowing. Sub-scores of the impaired patient group showed worsening for the glottal closure reflex when the endoscope touched the epiglottis or arytenoid, as well as a reduction in the extent of pharyngeal clearance following the ingestion of blue-dyed water. CONCLUSION: After TOVS, swallowing function is generally well preserved. Elderly patients, especially those with laryngeal hypoesthesia and poor clearance, are at risk of swallowing dysfunction.

[The clinical features of migraine-associated vertigo].

Migraine-associated vertigo (MAV) is proposed as a new clinical entity on the basis of the assumption that the typical migraine and vertigo or dizziness have a common pathophysiology. Some of the patients with recurrent vertigo syndromes with unknown pathology may have MAV. We performed a retrospective study to clarify the clinical characteristics of MAV in the Japanese population. The following were considered as diagnostic criteria: (1) recurrent vestibular symptoms, (2) migraine headache as defined by the International Headache Society (IHS) criteria, (3) at least one instance of synchronization of a vertiginous attack with a migraine headache, (4) no associated unilateral hearing loss, and (5) absence of other diseases that may have caused vertiginous attacks. Of 552 patients with dizziness or vertigo, 46 (8.3%) were diagnosed as having MAV. A typical feature of this clinical entity is that migraine occurs before the onset of vertigo in women aged 30-40 years. Usually the attacks occur once in a year for 1 to 10 years. An attack lasts for 1-24 h and presents as vertigo and unsteadiness with simultaneous headache. The presence of hearing loss presents an important clinical dilemma. Whether the condition in patients experiencing hearing loss should be defined as MAV or not is still a matter for discussion.

[Migraine-associated vertigo with hearing loss and recurrent vertigo attack].

The clinical features of Ménière's disease and migraine-associated vertigo are quite similar. Both disorders are characterized by repeated vertigo spells. Several diagnostic criteria are used to diagnose migraine-associated vertigo. None of these criteria has been internationally defined, although the criteria proposed by Neuhauser are wieldy accepted. Hearing impairment is believed to be a key factor for diagnosing Ménière's disease. We report herein on a case of repeated vertigo spells with sensorineural hearing loss in the right ear. Initially, the condition was diagnosed as Ménière's disease. Treatment for improving endolymphatic hydrops did not have an effect on the vertigo spells. On careful questioning, we noted the coexistence of migraines without any aura. Treatment with Ca antagonists to prevent the migraine attacks successfully stopped the patient's vertigo spells. On the basis of this clinical course, it is safe to assume that the patient had migraine-associated vertigo with sensorineural hearing loss rather than Ménière's disease. For a patient experiencing migraines together with sensorineural hearing loss, an accurate diagnosis requires careful evaluation. The coexistence of migraines should be carefully ruled out, even if Ménière's disease with hearing loss is strongly suspected.

[Two cases of pediatric psychogenic gait disturbance].

We report herein on 2 cases of pediatric psychogenic gait disturbance. Both patients (boys) were aged 10 years. Patient 1 had psychogenic fever and psychogenic visual disturbance. His symptoms improved after 4 months. Patient 2 had headache and general fatigue and was subfebrile. His symptoms disappeared after 5 months. Pediatric psychogenic gait disturbance is rare, and it is important to understand the clinical characteristics of the affected patients. In most cases, treatment can be time-consuming. To treat these patients, it is important to rule out organic disorders. A diagnosis of psychogenic gait disturbance should be made on the basis of the clinical characteristics of the disorder, such as (1) momentary fluctuations of stance and gait, often in response to suggestions; (2) excessive slowness or hesitation of locomotion incompatible with neurological disease; and (3) uneconomic postures with wastage of muscle energy. These symptoms typically improve in 4-5 months.

[Treatment of chronic subjective dizziness by SSRIs].

It has been reported that the dizziness or vertigo in about 10 to 30 patients visiting an otolaryngologist is of psychiatric origin. Since otolaryngologists are not familiar with the treatment for these patients, such treatment is usually not adequate. The clinical entity of chronic subjective dizziness (CSD) is one of psychiatric dizziness proposed by Staab and Ruckenstein. Fourteen percent (40/285) of patients were diagnosed as having psychiatric dizziness in Hino Municipal Hospital last year. Among them we had 7 cases with CSD. We report herein on the result of the clinical examinations and pharmacological treatment. In most of the cases, subjective symptoms were significantly improved after the pharmacological treatment with SSRIs (Serotonin reuptake inhibitors). From these results, CSD is important clinical entity treatable by otolaryngologist with SSRIs. To prescribe SSRIs, it is important to know the common adverse reactions associated with SSRIs. These include gastrointestinal symptoms including nausea and activation syndromes especially in early stage of treatment. CSD is an important clinical entity, which should be diagnosed and is treatable by otolaryngologists.

[Application of vestibular rehabilitation with an introduction session in patients with chronic dizziness].

Pharmacological and non-pharmacological approaches are the treatment options for dizzy patients. Vestibular exercises are a potential treatment option for intractable dizzy patients who do not respond to conventional drug therapy. The retention rate of exercises is quite important for a successful outcome. We organized vestibular exercise courses to improve the retention rate in the outpatient groups; these courses comprised introduction sessions with a clinical psychologist and rehabilitation sessions with a clinical technologist. It is unclear whether the effects of vestibular rehabilitation are based on the improvement of the psychological parameters of vestibular function. Therefore, we evaluated the functional mechanism of vestibular rehabilitation by using questionnaires and balance function tests. Our study comprised 16 patients with chronic dizziness. The patients performing the self-administered home-based vestibular exercise courses were supervised in small groups. The patients were taught that the exercises were to be performed 4 times a day at their respective homes. The symptoms of dizziness were evaluated using the Japanese version of the dizziness handicap inventory (DHI). Anxiety and depression levels were assessed using a set of psychological questionnaires. The static and dynamic balance function was assessed using static posturography and foam posturography and by measuring the time required for performing a certain series of eye-head movement protocols at the initial visit, before rehabilitation, and 2 and 3 months after rehabilitation. Of 16 patients, 15 could successfully complete the study (93.8%). The DHI score significantly improved 1 month after the rehabilitation, whereas anxiety and depression levels did not improve. The results of static and foam posturography as well as the time required for the eye-head movements also significantly improved. The improvement in the DHI scores was not associated with psychological changes, but with the improvement in the static and dynamic balance function.

Numerical Simulation of Nasal Resistance Using Three-dimensional Models of the Nasal Cavity and Paranasal Sinus.

OBJECTIVE: Previously, we used a nasal cavity model to analyze the intranasal airflow dynamics and numerically calculate the nasal resistance value. In this study, We attempted clarify the parameters influencing nasal resistance by newly developed computer model. METHODS: The computer simulation model was developed from the structures of nasal airway tract adopted from 1.0-mm slice computed tomography (CT) obtained from the 2 of the healthy volunteers. (model 1: the one at 35-year-old man, model 2: 25-year-old man.) We have calculated the nasal resistance by computer simulation calculations of both model 1 and model 2. These calculated values were compared with the values obtained from the established method of rhinomanometry. For the simulation, Fluent 17.2® (ANSYS, American) was employed for f luid a nalysis u sing the continuity equation for 3D incompressible flow and the Navies-Stokes equation for the basic equations. Both models were laminar models. The SIMPLE calculation method using the finite volume method was employed here, and the quadratic precision upwind difference method was used to discretize the convection terms. RESULTS: The measured (simulation) values in Model 1 were 0.69 (0.48), 1.10 (0.41), and 0.42 (0.22) Pa/cm3/s on the right, left, and both sides, whereas those in Model 2 were 0.72 (0.21), 0.32 (0.09), and 0.22 (0.06) Pa/cm3/s, respectively. CONCLUSION: Our results suggest that nasal resistance is possibly affected by the length of the inferior turbinate and the cross-sectional area of the choana and nasopharynx. Further experiments using additional nasal cavity and paranasal sinus models are warranted.

Malignant Lymphoma with the MRI Findings Mimicking Inflammatory Disease: A Case Report.

Magnetic resonance imaging (MRI) is a more useful diagnostic modality for detecting paranasal tumors compared with computed tomography (CT). We encountered a case of malignant lymphoma of the maxillary sinus. Although CT findings suggested malignancy, MRI findings indicated an inflammatory disease. The patient was a 51-year-old man with a chief complaint of right maxillary toothache. Edema in the right middle meatus and bloody rhinorrhea were observed. CT revealed r ight maxillary s inus shadow with partial bone loss, suggesting malignancy. However, MRI performed two weeks later showed an internal homogeneous lesion with neither contrast effect, nor invasion outside the maxillary sinus. The patient also had no fever, weight loss, or night sweats. Additionally, no palpable cervical lymphadenopathy was observed. Endoscopic sinus surgery was performed to confirm the diagnosis. Upon opening the maxillary sinus, highly viscous retention and a large amount of yellowish-white debris were observed. Allergic fungal rhinosinusitis was suspected. However, histopathological analysis of the debris established a diagnosis of malignant lymphoma. The debris exhibited pathological findings of necrosis. The patient remained in remission after undergoing radiochemotherapy. Malignant lymphomas of the paranasal sinuses, which have a minimal tendency for invasion but with considerable predominance of necrosis, may be diagnosed as an inflammatory disease, based on MRI findings. In cases in which a thorough physical examination could not rule out malignant lymphomas, an endoscopic biopsy should be immediately considered.

[Application of antidepressant to treat patients in the department of otolaryngology].

There are some patients complaining of somatic symptom who has depression. The use of antidepressant to these patients would be quite useful. Patients with dispersion have a variety sort of physical symptom. The evaluation of depression based on physical complaints may be difficult for otorhinolaryngologists, but it is important to do so where possible to increase the focus on the subject's physical illness. The prevalence of somatic complaints in hospitalized patients whose chief complaint was either dizziness or vertigo was very high. These patients were usually accompanied with depression. Then the effect of paroxetine to the patients with tinnitus was investigated. The paroxetine may be effective in treating distressed tinnitus patients with depression and anxiety by reducing their tinnitus severity as well as their depression and anxiety.

Crystal structure of plant ferritin reveals a novel metal binding site that functions as a transit site for metal transfer in ferritin.

Ferritins are important iron storage and detoxification proteins that are widely distributed in living kingdoms. Because plant ferritin possesses both a ferroxidase site and a ferrihydrite nucleation site, it is a suitable model for studying the mechanism of iron storage in ferritin. This article presents for the first time the crystal structure of a plant ferritin from soybean at 1.8-A resolution. The soybean ferritin 4 (SFER4) had a high structural similarity to vertebrate ferritin, except for the N-terminal extension region, the C-terminal short helix E, and the end of the BC-loop. Similar to the crystal structures of other ferritins, metal binding sites were observed in the iron entry channel, ferroxidase center, and nucleation site of SFER4. In addition to these conventional sites, a novel metal binding site was discovered intermediate between the iron entry channel and the ferroxidase site. This site was coordinated by the acidic side chain of Glu(173) and carbonyl oxygen of Thr(168), which correspond, respectively, to Glu(140) and Thr(135) of human H chain ferritin according to their sequences. A comparison of the ferroxidase activities of the native and the E173A mutant of SFER4 clearly showed a delay in the iron oxidation rate of the mutant. This indicated that the glutamate residue functions as a transit site of iron from the 3-fold entry channel to the ferroxidase site, which may be universal among ferritins.

Role of H-1 and H-2 subunits of soybean seed ferritin in oxidative deposition of iron in protein.

Naturally occurring phytoferritin is a heteropolymer consisting of two different H-type subunits, H-1 and H-2. Prior to this study, however, the function of the two subunits in oxidative deposition of iron in ferritin was unknown. The data show that, upon aerobic addition of 48-200 Fe(2+)/shell to apoferritin, iron oxidation occurs only at the diiron ferroxidase center of recombinant H1 (rH-1). In addition to the diiron ferroxidase mechanism, such oxidation is catalyzed by the extension peptide (a specific domain found in phytoferritin) of rH-2, because the H-1 subunit is able to remove Fe(3+) from the center to the inner cavity better than the H-2 subunit. These findings support the idea that the H-1 and H-2 subunits play different roles in iron mineralization in protein. Interestingly, at medium iron loading (200 irons/shell), wild-type (WT) soybean seed ferritin (SSF) exhibits a stronger activity in catalyzing iron oxidation (1.10 ± 0.13 µm iron/subunit/s) than rH-1 (0.59 ± 0.07 µm iron/subunit/s) and rH-2 (0.48 ± 0.04 µm iron/subunit/s), demonstrating that a synergistic interaction exists between the H-1 and H-2 subunits in SSF during iron mineralization. Such synergistic interaction becomes considerably stronger at high iron loading (400 irons/shell) as indicated by the observation that the iron oxidation activity of WT SSF is ∼10 times larger than those of rH-1 and rH-2. This helps elucidate the widespread occurrence of heteropolymeric ferritins in plants.

A novel EP-involved pathway for iron release from soya bean seed ferritin.

Iron in phytoferritin from legume seeds is required for seedling germination and early growth. However, the mechanism by which phytoferritin regulates its iron complement to these physiological processes remains unknown. In the present study, protein degradation is found to occur in purified SSF (soya bean seed ferritin) (consisting of H-1 and H-2 subunits) during storage, consistent with previous results that such degradation also occurs during seedling germination. In contrast, no degradation is observed with animal ferritin under identical conditions, suggesting that SSF autodegradation might be due to the EP (extension peptide) on the exterior surface of the protein, a specific domain found only in phytoferritin. Indeed, EP-deleted SSF becomes stable, confirming the above hypothesis. Further support comes from a protease activity assay showing that EP-1 (corresponding to the EP of the H-1 subunit) exhibits significant serine protease-like activity, whereas the activity of EP-2 (corresponding to the EP of the H-2 subunit) is much weaker. Consistent with the observation above, rH-1 (recombinant H-1 ferritin) is prone to degradation, whereas its analogue, rH-2, becomes very stable under identical conditions. This demonstrates that SSF degradation mainly originates from the serine protease-like activity of EP-1. Associated with EP degradation is a considerable increase in the rate of iron release from SSF induced by ascorbate in the amyloplast (pH range, 5.8-6.1). Thus phytoferritin may have facilitated the evolution of the specific domain to control its iron complement in response to cell iron need in the seedling stage.