Ultrasound imaging for evaluation of impalement-related injuries to the oral cavity in pediatric patients: a case series study

BACK GROUND

An impalement-related injury to the oral cavity is common in pediatric patients at emergency department. A computed tomography evaluation is not always suitable in these cases. Herein, we aimed to present oral sonography findings from six pediatric patients presenting with impalement-related injury to the oral cavity.

CASE SERIES

All included patients were younger than 4 years and sustained injuries with a toothbrush, chopstick, water gun, and fork to the tonsils, submandibular gland area, uvula, and under the tongue.

CONCLUSION

Ultrasound imaging appeared useful in helping diagnose impalement-related injuries lateral to the midline.

Regulation of the Stability and Localization of Post-synaptic Membrane Proteins by Liquid-Liquid Phase Separation

Synaptic plasticity is a cellular mechanism of learning and memory. The synaptic strength can be persistently upregulated or downregulated to update the information sent to the neuronal network and form a memory engram. For its molecular mechanism, the stability of α-amino-3-hydroxyl-5-methyl-4-isoxazolepropionate-type glutamate receptor (AMPAR), a glutamatergic ionotropic receptor, on the postsynaptic membrane has been studied for these two decades. Since AMPAR is not saturated on the postsynaptic membrane during a single event of neurotransmitter release, the number and nanoscale localization of AMPAR is critical for regulating the efficacy of synaptic transmission. The observation of AMPAR on the postsynaptic membrane by super-resolution microscopy revealed that AMPAR forms a nanodomain that is defined as a stable segregated cluster on the postsynaptic membrane to increase the efficacy of synaptic transmission. Postsynaptic density (PSD), an intracellular protein condensate underneath the postsynaptic membrane, regulates AMPAR dynamics via the intracellular domain of Stargazin, an auxiliary subunit of AMPAR. Recently, it was reported that PSD is organized by liquid-liquid phase separation (LLPS) to form liquid-like protein condensates. Furthermore, the calcium signal induced by the learning event triggers the persistent formation of sub-compartments of different protein groups inside protein condensates. This explains the formation of nanodomains via synaptic activation. The liquid-like properties of LLPS protein condensates are ideal for the molecular mechanism of synaptic plasticity. In this review, we summarize the recent progress in the properties and regulation of synaptic plasticity, postsynaptic receptors, PSD, and LLPS.

Arc self-association and formation of virus-like capsids are mediated by an N-terminal helical coil motif

Activity-regulated cytoskeleton-associated protein (Arc) is a protein interaction hub with diverse roles in intracellular neuronal signaling, and important functions in neuronal synaptic plasticity, memory, and postnatal cortical development. Arc has homology to retroviral Gag protein and is capable of self-assembly into virus-like capsids implicated in the intercellular transfer of RNA. However, the molecular basis of Arc self-association and capsid formation is largely unknown. Here, we identified a 28-amino-acid stretch in the mammalian Arc N-terminal (NT) domain that is necessary and sufficient for self-association. Within this region, we identified a 7-residue oligomerization motif, critical for the formation of virus-like capsids. Purified wild-type Arc formed capsids as shown by transmission and cryo-electron microscopy, whereas mutant Arc with disruption of the oligomerization motif formed homogenous dimers. An atomic-resolution crystal structure of the oligomerization region peptide demonstrated an antiparallel coiled-coil interface, strongly supporting NT-NT domain interactions in Arc oligomerization. The NT coil-coil interaction was also validated in live neurons using fluorescence lifetime FRET imaging, and mutation of the oligomerization motif disrupted Arc-facilitated endocytosis. Furthermore, using single-molecule photobleaching, we show that Arc mRNA greatly enhances higher-order oligomerization in a manner dependent on the oligomerization motif. In conclusion, a helical coil in the Arc NT domain supports self-association above the dimer stage, mRNA-induced oligomerization, and formation of virus-like capsids. DATABASE: The coordinates and structure factors for crystallographic analysis of the oligomerization region were deposited at the Protein Data Bank with the entry code 6YTU.

Shank3 Binds to and Stabilizes the Active Form of Rap1 and HRas GTPases via Its NTD-ANK Tandem with Distinct Mechanisms

Shank1/2/3, major scaffold proteins in excitatory synapses, are frequently mutated in patients with psychiatric disorders. Although the Shank N-terminal domain and ankyrin repeats domain tandem (NTD-ANK) is known to bind to Ras and Rap1, the molecular mechanism underlying and functional significance of the bindings in synapses are unknown. Here, we demonstrate that Shank3 NTD-ANK specifically binds to the guanosine triphosphate (GTP)-bound form of HRas and Rap1. In addition to the canonical site mediated by the Ras-association domain and common to both GTPases, Shank3 contains an unconventional Rap1 binding site formed by NTD and ANK together. Binding of Shank3 to the GTP-loaded Rap1 slows down its GTP hydrolysis by SynGAP. We further show that the interactions between Shank3 and HRas/Rap1 at excitatory synapses are promoted by synaptic activation. Thus, Shank3 may be able to modulate signaling of the Ras family proteins via directly binding to and stabilizing the GTP-bound form of the enzymes.

Stoichiometry and phosphoisotypes of hippocampal AMPA-type glutamate receptor phosphorylation

It has been proposed that the AMPAR phosphorylation regulates trafficking and channel activity, thereby playing an important role in synaptic plasticity. However, the actual stoichiometry of phosphorylation, information critical to understand the role of phosphorylation, is not known because of the lack of appropriate techniques for measurement. Here, using Phos-tag SDS-PAGE, we estimated the proportion of phosphorylated AMPAR subunit GluA1. The level of phosphorylated GluA1 at S831 and S845, two major sites implicated in AMPAR regulation, is almost negligible. Less than 1% of GluA1 is phosphorylated at S831 and less than 0.1% at S845. Considering the number of AMPAR at each synapse, the majority of synapses do not contain any phosphorylated AMPAR. Also, we did not see evidence of GluA1 dually phosphorylated at S831 and S845. Neuronal stimulation and learning increased phosphorylation, but the proportion was still low. Our results impel us to reconsider the mechanisms underlying synaptic plasticity.

Phosphorylation of cyclin-dependent kinase 5 (Cdk5) at Tyr-15 is inhibited by Cdk5 activators and does not contribute to the activation of Cdk5

Cdk5 is a member of the cyclin-dependent kinase (Cdk) family. In contrast to other Cdks that promote cell proliferation, Cdk5 plays a role in regulating various neuronal functions, including neuronal migration, synaptic activity, and neuron death. Cdks responsible for cell proliferation need phosphorylation in the activation loop for activation in addition to binding a regulatory subunit cyclin. Cdk5, however, is activated only by binding to its activator, p35 or p39. Furthermore, in contrast to Cdk1 and Cdk2, which are inhibited by phosphorylation at Tyr-15, the kinase activity of Cdk5 is reported to be stimulated when phosphorylated at Tyr-15 by Src family kinases or receptor-type tyrosine kinases. We investigated the activation mechanism of Cdk5 by phosphorylation at Tyr-15. Unexpectedly, however, it was found that Tyr-15 phosphorylation occurred only on monomeric Cdk5, and the coexpression of activators, p35/p25, p39, or Cyclin I, inhibited the phosphorylation. In neuron cultures, too, the activation of Fyn tyrosine kinase did not increase Tyr-15 phosphorylation of Cdk5. Further, phospho-Cdk5 at Tyr-15 was not detected in the p35-bound Cdk5. In contrast, expression of active Fyn increased p35 in neurons. These results indicate that phosphorylation at Tyr-15 is not an activation mechanism of Cdk5 but, rather, indicate that tyrosine kinases could activate Cdk5 by increasing the protein amount of p35. These results call for reinvestigation of how Cdk5 is regulated downstream of Src family kinases or receptor tyrosine kinases in neurons, which is an important signaling cascade in a variety of neuronal activities.

Noninvasive estimation of fibrosis progression overtime using the FIB-4 index in chronic hepatitis C

The FIB-4 index is a simple formula to predict liver fibrosis based on the standard biochemical values (AST, ALT and platelet count) and age. We here investigated the utility of the index for noninvasive prediction of progression in liver fibrosis. The time-course alteration in the liver fibrosis stage between paired liver biopsies and the FIB-4 index was examined in 314 patients with chronic hepatitis C. The average interval between liver biopsies was 4.9 years. The cases that showed a time-course improvement in the fibrosis stage exhibited a decrease in the FIB-4 index, and those that showed deterioration in the fibrosis stage exhibited an increase in the FIB-4 index with a significant correlation (P < 0.001). Increase in the ΔFIB-4 index per year was an independent predictive factor for the progression in liver fibrosis with an odds ratio of 3.90 (P = 0.03). The area under the receiver operating characteristic curve of the ΔFIB-4 index/year for the prediction of advancement to cirrhosis was 0.910. Using a cut-off value of the ΔFIB-4 index/year <0.4 or ≥ 0.4, the cumulative incidence of fibrosis progression to cirrhosis at 5 and 10 years was 34% and 59%, respectively in patients with the ΔFIB-4 index/year ≥0.4, whereas it was 0% and 3% in those with the ΔFIB-4 index/year <0.4 (P < 0.001). In conclusion, measurement of the time-course changes in the FIB-4 index is useful for the noninvasive and real-time estimation of the progression in liver fibrosis.

Protein kinase Czeta regulates Cdk5/p25 signaling during myogenesis

Atypical protein kinase Cζ (PKCζ) is emerging as a mediator of differentiation. Here, we describe a critical role for PKCζ during myogenic differentiation. Our results identify PKCζ as a controller of myogenic differentiation by its regulation of Cdk5.

Atypical protein kinase Cζ (PKCζ) is emerging as a mediator of differentiation. Here, we describe a novel role for PKCζ in myogenic differentiation, demonstrating that PKCζ activity is indispensable for differentiation of both C2C12 and mouse primary myoblasts. PKCζ was found to be associated with and to regulate the Cdk5/p35 signaling complex, an essential factor for both neuronal and myogenic differentiation. Inhibition of PKCζ activity prevented both myotube formation and simultaneous reorganization of the nestin intermediate filament cytoskeleton, which is known to be regulated by Cdk5 during myogenesis. p35, the Cdk5 activator, was shown to be a specific phosphorylation target of PKCζ. PKCζ-mediated phosphorylation of Ser-33 on p35 promoted calpain-mediated cleavage of p35 to its more active and stable fragment, p25. Strikingly, both calpain activation and the calpain-mediated cleavage of p35 were shown to be PKCζ-dependent in differentiating myoblasts. Overall, our results identify PKCζ as a controller of myogenic differentiation by its regulation of the phosphorylation-dependent and calpain-mediated p35 cleavage, which is crucial for the amplification of the Cdk5 activity that is required during differentiation.

Quantitative measurement of in vivo phosphorylation states of Cdk5 activator p35 by Phos-tag SDS-PAGE

Phosphorylation is a major post-translational modification widely used in the regulation of many cellular processes. Cyclin-dependent kinase 5 (Cdk5) is a proline-directed serine/threonine kinase activated by activation subunit p35. Cdk5-p35 regulates various neuronal activities such as neuronal migration, spine formation, synaptic activity, and cell death. The kinase activity of Cdk5 is regulated by proteolysis of p35: proteasomal degradation causes down-regulation of Cdk5, whereas cleavage of p35 by calpain causes overactivation of Cdk5. Phosphorylation of p35 determines the proteolytic pathway. We have previously identified Ser(8) and Thr(138) as major phosphorylation sites using metabolic labeling of cultured cells followed by two-dimensional phosphopeptide mapping and phosphospecific antibodies. However, these approaches cannot determine the extent of p35 phosphorylation in vivo. Here we report the use of Phos-tag SDS-PAGE to reveal the phosphorylation states of p35 in neuronal culture and brain. Using Phos-tag acrylamide, the electrophoretic mobility of phosphorylated p35 was delayed because it is trapped at Phos-tag sites. We found a novel phosphorylation site at Ser(91), which was phosphorylated by Ca(2+)-calmodulin-dependent protein kinase II in vitro. We constructed phosphorylation-dependent banding profiles of p35 and Ala substitution mutants at phosphorylation sites co-expressed with Cdk5 in COS-7 cells. Using the standard banding profiles, we assigned respective bands of endogenous p35 with combinations of phosphorylation states and quantified Ser(8), Ser(91), and Thr(138) phosphorylation. The highest level of p35 phosphorylation was observed in embryonic brain; Ser(8) was phosphorylated in all p35 molecules, whereas Ser(91) was phosphorylated in 60% and Thr(138) was phosphorylated in approximately 12% of p35 molecules. These are the first quantitative and site-specific measurements of phosphorylation of p35, demonstrating the usefulness of Phos-tag SDS-PAGE for analysis of phosphorylation states of in vivo proteins.

Differential regulation of the Cdk5-dependent phosphorylation sites of inhibitor-1 and DARPP-32 by depolarization

While cyclin-dependent kinase 5 (Cdk5) is of growing importance to neuronal signaling, its regulation remains relatively unexplored. Examination of the mechanism by which NMDA modulates the phosphorylation of protein phosphatase inhibitor-1 at Ser6 and Ser67 and dopamine- and cAMP-regulated phosphoprotein M(r) 32 000 at Thr75 revealed that generalized depolarization, rather than specific activation of NMDA receptors, was sufficient to induce decreases in these Cdk5 sites. Although no evidence for the involvement of the Cdk5 cofactors p35 or p39, or for L- and T-type voltage-gated Ca(2+) channels, was found, evaluation of the role of phosphatases and extracellular cations revealed differential regulation of the three sites. NMDA-induced decreases in the phosphorylation of Thr75 of dopamine- and cAMP-regulated phosphoprotein M(r) 32 000 required protein phosphatase 1/2A activity and extracellular Ca(2+). In contrast, the effects on Ser6 and Ser67 of inhibitor-1 were not cation specific; either Na(+) or Ca(2+) sufficed. Furthermore, while the decrease in phosphorylation of Ser6 was partially dependent on protein phosphatase 2B, that of Ser67 was independent of the major protein serine/threonine phosphatases, likely indicating the presence of a pathway by which NMDA inhibits Cdk5 activity. Thus, in the striatum the regulation of phosphorylation of Cdk5-dependent sites by NMDA occurs through multiple distinct pathways.

Pharmacokinetics and enhanced PKR response in patients with chronic hepatitis C treated with pegylated interferon alpha-2b and ribavirin

This study investigated the molecular and pharmacokinetic mechanisms of the enhanced antiviral efficacy associated with pegylated interferon (PEG-IFN) alpha-2b and ribavirin. The study involved comparing the expression of serial double-stranded RNA-activated protein kinase (PKR) before and during treatment in 26 PEG-IFN alpha-2b and 26 conventional IFN alpha-2b recipients matched for age, body weight and dose of ribavirin. The pharmacokinetics of PEG-IFN alpha-2b and ribavirin was analysed in 15 of the 26 PEG-IFN recipients. There was a rapid increase in PKR expression in both treatment groups, although expression from day 2 onwards was maintained at a significantly higher level in the PEG-IFN recipients (P < 0.05). C(max) of PEG-IFN occurred 12-48 h after the initial administration, with t(1/2) and C(min) being 49 h and 190 pg/mL, respectively. In contrast to ribavirin, accumulation of PEG-IFN was minimal. There was no association between serum PEG-IFN and ribavirin levels and virological response. Although baseline expression of PKR before treatment was marginally higher in nonresponders (NRs), from day 2 onwards, sequential PKR expression in response to PEG-IFN was higher in sustained viral responders compared with the NRs (P < 0.05). Significant correlations were found between kinetics of PKR expression and viral decline rates in each phase of hepatitis C virus dynamics (first phase, r = 0.67, P = 0.0006; second phase, r = 0.67, P = 0.001). In conclusion, improvement in pharmacokinetics following pegylation led to higher intracellular PKR expression, which was associated with enhanced virological efficacy of PEG-IFN-based combination therapy. The concentrations of both ribavirin and PEG-IFN alpha-2b were not associated with viral response and PKR expression.

p25/cyclin-dependent kinase 5 promotes the progression of cell death in nucleus of endoplasmic reticulum-stressed neurons

Dysregulation of cyclin-dependent kinase 5 (Cdk5) by cleavage of its activator p35 to p25 by calpain is involved in the neuronal cell death observed in neurodegenerative disorders, including Alzheimer's disease. However, it is not yet clear how p25/Cdk5 induces cell death, although its cytosolic localization or extended half life are thought to be involved. We show here that endoplasmic reticulum (ER) stress causes the calpain-dependent cleavage of p35 to p25 in primary cultured cortical neurons. Generation of p25 occurred at a cell death execution step in ER-stressed neurons. p25 translocated to the nucleus in ER-stressed neurons, whereas p35/Cdk5 was perinuclear in control neurons. Cdk5 inhibitors or dominant-negative Cdk5 suppressed ER stress-induced neuronal cell death. These findings indicate that p25/Cdk5 is a proapoptotic factor that promotes ER stress-induced neuronal cell death in nuclei.

Enhanced activation of Ca2+/calmodulin-dependent protein kinase II upon downregulation of cyclin-dependent kinase 5-p35

Cyclin-dependent kinase 5 (Cdk5)-p35 is downregulated in cultured neurons by N-methyl-D-aspartate (NMDA) via the proteasomal degradation of p35. However, it is not known where in neurons this downregulation occurs or the physiologic meaning of the reaction. We show the enrichment of Cdk5 and p35 in the postsynaptic density and the NMDA-induced degradation of postsynaptic p35 using brain slices and cultured neurons. To evaluate the role of this downregulation, we examined the relationship between Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) activation and Cdk5 downregulation, as events downstream from NMDA stimulation. Glutamate or NMDA stimulation induced CaMKII autophosphorylation over a time course that mirrored the time course of p35 degradation. To simulate the downregulation of postsynaptic Cdk5 in invitro experiments, we used the Cdk5 inhibitor roscovitine. The inhibition of Cdk5 activity by roscovitine enhanced CaMKII autophosphorylation and activation in cultured neurons, and in an isolated postsynaptic-density-enriched fraction. These results suggest that Cdk5 activity suppresses CaMKII activation, and that the downregulation of Cdk5 activity after treatment withNMDA facilitates CaMKII activation, leading to the easier induction of long-term potentiation.

Personality and cancer survival: the Miyagi cohort study

We tested the hypothesis that personality plays a role in cancer outcome in a population-based prospective cohort study in Japan. In July 1990, 41 442 residents of Japan completed a short form of the Eysenck Personality Questionnaire-Revised and a questionnaire on various health habits, and between January 1993 and December 1997, 890 incident cases of cancer were identified among them. These 890 cases were followed up until March 2001, and a total of 356 deaths from all causes was identified among them. Cox proportional-hazards regression was used to estimate the hazard ratio (HR) of death according to four score levels on each of four personality subscales (extraversion, neuroticism, psychoticism, and lie), with adjustment for potential confounding factors. Multivariable HRs of deaths from all causes for individuals in the highest score level on each personality subscale compared with those at the lowest level were 1.0 for extraversion (95% CI=0.8–1.4; Trend P=0.73), 1.1 for neuroticism (0.8–1.6; Trend P=0.24), 1.2 for psychoticism (0.9–1.6; Trend P=0.29), and 1.0 for lie (0.7–1.5; Trend P=0.90). The data obtained in this population-based prospective cohort study in Japan do not support the hypothesis that personality is associated with cancer survival.

The number of CD10-positive glomerular epithelial cells reflects renal prognosis in IgA nephropathy patients

BACKGROUND

The glomerular epithelial cells play an important role in glomerular filtration of the kidney. The disruption of these cells contributes to the development of glomerulosclerosis. The present study was performed to elucidate whether loss of the glomerular epithelial cells is associated with renal injury in patients with IgA nephropathy.

PATIENTS AND METHODS

Thirty renal biopsy specimens from IgA nephropathy, 12 from minor glomerular abnormalities and 5 from normal controls were observed. The specimens from IgA nephropathy were divided into 2 groups: Group IgA-1, including 11 patients who had received a follow-up renal biopsy because of deterioration of renal function, and Group IgA-2, consisting of the remaining 19 patients without follow-up biopsy. Immunohistochemistry was performed using a monoclonal antibody against CD10 antigen that appears on mature epithelial cells of glomeruli.

RESULTS

The average number of CD10-positive glomerular epithelial cells (GECs) was significantly lower in IgA nephropathy than in either minor glomerular abnormalities or the normal controls. In IgA nephropathy, there were significant correlations of the GECs with renal functions. The GECs were reduced along with the progression of histopathological damage. In group IgA-1, the GECs were significantly reduced at the second biopsy compared with the first biopsy, and significantly fewer in group IgA-1 than in group IgA-2 at the first biopsy. The GECs showed a significant correlation with renal prognosis during the follow-up period.

CONCLUSIONS

The reduction of GECs was associated with renal dysfunction, histopathological damage and renal prognosis. The GECs may be a useful predictor of renal prognosis in IgA nephropathy.

Immunohistochemical study of macrophage migration inhibitory factor in rat liver fibrosis induced by thioacetamide

Macrophage migration inhibitory factor (MIF) is a molecule known to regulate macrophage accumulation at sites of inflammation. To elucidate the role of MIF in progression of liver fibrosis, the immunohistochemical localization of MIF and macrophages in the liver were examined. Male Wistar rats received thioacetamide (TA) injections (200 mg/kg, i.p.) for 1 or 6 weeks. In biochemical and histological tests, it was confirmed that liver fibrosis was induced. In immunohistochemical analyses, the expression of MIF protein was seen in hepatocytes in the areas extending out from the central veins to the portal tracts. In particular, at 6 weeks, immunoreactivity was detected in degenerated hepatocytes adjacent to the fibrotic areas but hardly observed in the fibrotic areas. On the other hand, a number of exudate macrophages stained by antibody ED1 were seen in the areas from the central veins to the portal tracts at 1 week and in the fibrotic areas at 6 weeks. Macrophages also showed a significant increase in number as compared with controls. These results revealed that there was a close relationship between the appearance of MIF expression and ED1-positive exudate macrophages in degenerated hepatocytes during the progression of TA-induced liver fibrosis.

Effect of trichloroethylene on spatiotemporal pattern of LTP in mouse hippocampal slices

The effect of trichloroethylene (TCE) on long-term potentiation (LTP) was studied using both electrical and optical recording. The hippocampi from mice injected with 300 mg/kg or 1000 mg/kg TCE were sliced 24 h after administration. The field potential from the CAI was recorded. After the application of tetanus, population spikes (PS) were potentiated in all groups, but the post-per-pre ratio of PS was smaller in TCE groups than in the control. Optical recording was also carried out in 1000 mg/kg TCE-injected mice and a new analytical method using a high speed camera was employed. After the induction of tetanus, the optical signal was potentiated in both TCE and control groups. However, the post-per-pre ratio of the optical signals and response area were smaller in the TCE groups than in the control. It was suggested that the impairment of LTP is one of the mechanisms of the impairment of immediate memory after acute exposure to TCE in humans.

[A case of rheumatoid arthritis associated with minimal change nephrotic syndrome]

A 55-year-old Japanese woman has been treated with various kinds of anti-rheumatic drugs under a diagnosis of rheumatoid arthritis(RA) for 18 years of disease duration. She persistently had right elbow joint pain and swelling and X-ray showed bone erosion on humerus. Thus, the synovectomy was performed with typical histopathology of RA on April 1999. On the end of February 2000, she had suddenly fatigue and anasarca with profound proteinuria of nephrotic syndrome. The renal biopsy showed minimal change glomerulopathy and no cellular infiltration in interstitial tissue by light microscopy and partial fusion of foot process by electron microscopy. Renal function was sustained normally. All of anti-rheumatic drugs including D-penicillamine(D-Pc) except NSAID were stopped and she was treated with bed rest, diet therapy, diuretics and albumin infusion without steroid therapy. Edema and proteinuria gradually disappeared. Membranous and amyloid nephropathy in RA patients associated with nephrotic syndrome are found in high incidence in literature. In low incidence, MCNS is associated with NSAID or D-Pc induced nephropathy in RA. In our case, nephrotic syndrome disappeared in 6 weeks without discontinuation of NSAID and application of steroid therapy. Thus, MCNS might be co-incidentally associated with RA.

New model of oropharyngeal candidiasis in mice

We established a straightforward murine model of oropharyngeal candidiasis. Mice were immunosuppressed with cortisone acetate, anesthetized, and then inoculated by placing cotton wool balls saturated with Candida albicans sublingually for 2 h. A prolonged, reproducible infection was induced. This model may be useful for antifungal screening or pathogenesis studies.

Iron deposition in renal biopsy specimens from patients with kidney diseases

This study was performed to investigate the correlation between clinical parameters and grading of iron deposition in renal biopsy specimens from 102 patients with various kidney diseases. Iron deposition in renal tissues was detected by Berlin blue staining. The extent of iron staining was semiquantitatively graded as negative (Fe(-)), grade 0, or positive (Fe(+)), including faint, grade 1; moderate, grade 2; or severe, grade 3, by light microscopy. Thirty-four of 102 patients (33%) showed positive iron staining. Fe(+) patients had various renal diseases, mainly consisting of 12 patients with immunoglobulin A nephropathy and 5 patients with benign nephrosclerosis. Mean arterial pressure (MAP), serum creatinine (sCr) levels, incidence of hematuria, and urinary N-acetylbeta-D-glucosaminidase (u-NAG) levels in Fe(+) patients were significantly greater than those in Fe(-) patients, and u-NAG levels correlated positively with the extent of iron deposition. Study patients were tentatively divided into two groups according to the extent of iron deposition: group A, patients with grades 2 and 3 staining, and group B, patients with grades 0 and 1 staining. In group A, MAP, sCr level, urinary protein excretion, and the incidence of hematuria were significantly greater than in group B. Our results suggest that the amount of iron deposition in renal tissue may contribute to the progression of chronic renal disease and may be an early and sensitive indicator of renal damage in certain renal diseases.