A case report of undetected cardiac arrest in a patient with an insertable cardiac monitor.

Insertable cardiac monitors (ICMs) are small electrocardiographs implanted subcutaneously to automatically record electrocardiograms when arrhythmia is detected in patients with syncope. If the ICM misses a significant arrhythmia, it may delay the diagnosis of arrhythmogenic syncope and put the patient at risk. Herein, we describe a case of undetected cardiac arrest in a patient with ICM. An 87-year-old man with syncope was admitted to the hospital. After 8 days of monitoring, the cause could not be determined, and an ICM was implanted. Nine hours after implantation, the patient experienced cardiopulmonary arrest. Despite a body surface electrocardiogram showing ventricular flatline and fibrillation, the ICM failed to record. The cause of failure to record was considered to be the fluctuation in the R-wave amplitude of the ICM and noise oversensing. In conclusion, albeit infrequently, ICMs might overlook life-threatening arrhythmias. Even in cases where the ICM fails to detect an arrhythmia matching the symptoms, it may not be feasible to entirely rule out the presence of arrhythmias. Learning objective: Insertable cardiac monitors (ICMs) are used to diagnose arrhythmogenic syncope. However, extremely infrequently, ICM may fail to record life-threatening arrhythmias. Failure to capture arrhythmias can happen due to an unfortunate combination of factors such as a low amplitude of the recorded R wave and noise. Even in cases where the ICM does not detect an arrhythmia that matches the symptoms, it may not be feasible to completely exclude the presence of arrhythmias.

Colocalization of TDP-43 and stress granules at the early stage of TDP-43 aggregation in amyotrophic lateral sclerosis.

TDP-43 aggregates (skeins and round inclusions [RIs]) are frequent histopathological features of amyotrophic lateral sclerosis (ALS). We have shown that diffuse punctate cytoplasmic staining (DPCS) is the earliest pathologic manifestation of TDP-43 in ALS, corresponding to nonfibrillar TDP-43 located in the rough endoplasmic reticulum. Previous in vitro studies have suggested that TDP-43 inclusions may be derived from stress granules (SGs). Therefore, we investigated the involvement of SGs in the formation of TDP-43 inclusions. Formalin-fixed spinal cords of six ALS patients with a disease duration of less than 1 year (short duration), eight patients with a disease duration of 2-5 years (standard duration), and five normal controls were subjected to histopathological examination using antibodies against an SG marker, HuR. In normal controls, the cytoplasm of anterior horn cells was diffusely HuR-positive. In short-duration and standard-duration ALS, the number of HuR-positive anterior horn cells was significantly decreased relative to the controls. DPCS and RIs were more frequent in short-duration ALS than in standard-duration ALS. The majority of DPCS areas and a small proportion of RIs, but not skeins, were positive for HuR. Immunoelectron microscopy showed that ribosome-like granular structures in DPCS areas and RIs were labeled with anti-HuR, whereas skeins were not. These findings suggest that colocalization of TDP-43 and SGs occurs at the early stage of TDP-43 aggregation.

Cultivation of Piezotolerant and Piezophilic Hyperthermophiles with a Newly Developed Constant High Pressure and Temperature Culturing and Monitoring System.

The Earth's microbial biosphere extends from ambient to extreme environments, including deep-sea hydrothermal vents and subseafloor habitats. Despite efforts to understand the physiological adaptations of these microbes, our knowledge is limited due to the technological challenges associated with reproducing in situ high temperature (HT)-high hydrostatic pressure (HHP) conditions and sampling HT-HHP cultures. In the present study, we developed a new high temperature and pressure (HTP) incubation system that enabled the maintenance of HT-HHP conditions while sampling incubation medium and mostly eliminated non-biological reactions, including hydrogen generation or the leakage of small gaseous molecules. The main characteristics of our system are (1) a chamber made of gold with gold-etched lid parts that suppress the majority of non-biological reactions, (2) the exceptional containment of dissolved gas, even small molecules, such as hydrogen, and (3) the sampling capacity of intra-chamber liquid without depressurization and the isobaric transfer of a culture to inoculate new medium. We initially confirmed the retention of dissolved hydrogen in the incubation container at 82°C and 20| |MPa for 9 days. Cultivation tests with an obligate hyperthermophilic piezophile (Pyrococcus yayanosii), hydrogenotrophic hyperthermophile (Archaeoglobus profundus), and heterotrophic hyperthermophile (Pyrococcus horikoshii) were successful based on growth monitoring and chemical ana-lyses. During HTP cultivation, we observed a difference in the duration of the lag phase of P. horikoshii, which indicated the potential effect of a pressure change on the physiology of piezophiles. The present results suggest the importance of a cultivation system designed and developed explicitly for HTP conditions with the capacity for sampling without depressurization of the entire system.

Axon terminal hypertrophy of striatal projection neurons with levodopa-induced dyskinesia priming.

Background: A rat model of levodopa-induced dyskinesia (LID) showed enlarged axon terminals of striatal direct pathway neurons in the internal segment of the globus pallidus (GPi) with excessive gamma-aminobutyric acid (GABA) storage in them. Massive GABA release to GPi upon levodopa administration determines the emergence of LID. Objectives: We examined whether LID and axon terminal hypertrophy gradually develop with repeated levodopa treatment in Parkinsonian rats to examine if the hypertrophy reflects dyskinesia priming. Methods: 6-hydroxydopamine-lesioned hemiparkinsonian rats were randomly allocated to receive saline injections (placebo group, 14 days; n = 4), injections of 6 mg/kg levodopa methyl ester combined with 12.5 mg/kg benserazide (levodopa-treated groups, 3-day-treatment; n = 4, 7-day-treatment; n = 4, 14-day-treatment; n = 4), or injections of 6 mg/kg levodopa methyl ester with 12.5 mg/kg benserazide and 1 mg/kg 8-hydroxy-2-(di-n-propylamino)tetralin for 14 days (8-OH-DPAT-treated group; n = 4). We evaluated abnormal involuntary movement (AIM) scores and axon terminals in the GPi. Results: The AIM score increased with levodopa treatment, as did the hypertrophy of axon terminals in the GPi, showing an increased number of synaptic vesicles in hypertrophied terminals. Conclusion: Increased GABA storage in axon terminals of the direct pathway neurons represents the priming process of LID.

Effects of a Pharmacist-Led Educational Interventional Program on Electronic Monitoring-assessed Adherence to Direct Oral Anticoagulants: A Randomized, Controlled Trial in Patients with Nonvalvular Atrial Fibrillation.

PURPOSE: Several landmark trials have reported that direct oral anticoagulants (DOACs) are more effective in preventing stroke and systemic embolism than vitamin K antagonists. However, nonadherence to DOACs worsens prognosis in patients with nonvalvular atrial fibrillation (NVAF) despite the effectiveness of the drugs. The purpose of this study was to evaluate the effects of a pharmacist-led educational interventional program involving motivational interviewing on medication adherence, as assessed by electronic monitoring, in patients receiving DOACs for the treatment of NVAF. METHODS: This prospective, randomized, interventional study was conducted at outpatient cardiology clinics at general hospitals and pharmacies in Japan. Patients with NVAF who were treated with a once-daily DOAC (edoxaban) or a twice-daily DOAC (apixaban) were randomized to receive either: (1) an educational interventional program involving motivational interviewing regarding adherence to anticoagulants; or (2) standard medication counseling. The primary end point was the change in the medication adherence rate, calculated as the number of days that patients appropriately took the drug, as assessed by an electronic monitoring device, divided by the total number of days that the drug was prescribed, from a 12-week observation period to a 12-week intervention period. The secondary end points were tolerability outcomes. The effect of the educational interventional program on the primary end point was analyzed in subgroups stratified by gender and type of DOAC received. FINDINGS: A total of 268 patients completed the observation period and were randomly assigned to one of the two study groups. The difference in the primary end point between the educational interventional program group and the standard medication counseling group was not significant (mean [SD], 2.9% [7.5%] vs 3.4% [8.3%]). On multiple linear regression analysis, the difference in DOAC adherence between the two groups was not significant, but that adherence to apixaban was significantly improved among men in the educational interventional program (ß = 0.219; P = 0.012). Two patients died of causes considered unrelated to treatment; no stroke/systemic embolism or major bleeding events were observed. IMPLICATIONS: In this randomized, controlled study of the effects of a pharmacist-led educational interventional program using motivational interviewing on adherence to DOACs among patients with NVAF, adherence to DOACs, as assessed using an electronic monitoring device, was not improved with the educational interventional program compared to standard medication counseling . However, adherence to twice-daily apixaban was improved among men, but not among women, in the educational interventional program group. In this study, the selection of DOACs was not randomized, and the lack of assessment of the association between adherence to DOACs and clinical outcomes was a limitation. Japan Registry of Clinical Trials (jRCT) indentifier: jRCTs031180142.

Phosphorylation of Tau at Threonine 231 in Patients With Multiple System Atrophy and in a Mouse Model.

Multiple system atrophy (MSA) is a sporadic neurodegenerative disorder pathologically characterized by the presence of glial cytoplasmic inclusions (GCIs). Some MSA patients exhibit motor deficits with accompanying cognitive impairment. Of note, some patients suffering from MSA with longer disease duration have AT8-positive signals, which correspond to phosphorylated tau (P-tau) at 202/205 (P-tau202/205). However, P-tau sites other than the AT8 antibody epitope antibody are less well studied. Here, we focused on the effect of α-synuclein (Syn) expression on the phosphorylation of tau in MSA model mice. Among the 6 kinds of antibodies against P-tau, we confirmed that antibodies against P-tau at 231 (P-tau231) were phospho-specific and found that P-tau231 level was increased in parallel with disease progression in MSA model mice. Additional studies of human brains revealed that P-tau231 was mainly expressed in the temporal cortex in MSA brains and that its expression level was significantly higher in MSA patients than in controls. Immunohistochemical analysis showed that anti-P-tau231-, but not AT8, antibodies mainly immunolabeled hippocampal CA2/3 pyramidal neurons, and some GCIs in MSA. These data suggest that P-tau231 occurs in MSA differently from P-tau202/205.

Alteration of Vesicle-Associated Membrane Protein-Binding Protein B in α-Synuclein Aggregates in Lewy Body Disease.

α-Synuclein (α-Syn) binds to vesicle-associated membrane protein-binding protein B (VAPB) in the endoplasmic reticulum membrane. Recent studies have shown that α-Syn-immunoreactive Lewy pathology is characterized by membrane crowding, including vesicular structures. To elucidate the role of VAPB and vesicular structures in Parkinson's disease (PD) and in dementia with Lewy bodies (DLB), the relationships among VAPB, vesicular structures, and Lewy pathology were investigated by immunohistochemistry and immunoelectron microscopy in 8 PD and 4 DLB autopsy cases. The proportions of VAPB-negative neurons in the substantia nigra in PD and in the temporal cortex in DLB were significantly higher than those in 5 controls. In PD, the incidence of α-Syn inclusions in VAPB-negative neurons was significantly higher (77.4%) than in VAPB-positive neurons (1.6%) in the substantia nigra. In DLB, the incidence of α-Syn inclusions in VAPB-negative neurons was also significantly higher (65.3%) than in VAPB-positive neurons (2.8%) in the temporal cortex. Immunoelectron microscopy revealed that α-Syn and VAPB were localized to filamentous structures of Lewy bodies (LBs). However, only a few vesicular structures labeled with anti-α-Syn were observed within LBs. These findings suggest that reduction of VAPB is involved in the disease processes of PD and DLB, although vesicular structures may not directly contribute to the formation of LBs.

Involvement of autophagic protein DEF8 in Lewy bodies.

Dysregulation of autophagy, one of the major processes through which abnormal proteins are degraded, is a cardinal feature of synucleinopathies, including Lewy body diseases [Parkinson's disease (PD) and dementia with Lewy bodies (DLB)] and multiple system atrophy (MSA), which are characterized by the presence of abnormal α-synuclein in neurons and glial cells. Although several research groups have reported that Rubicon family proteins can regulate autophagosome-lysosome fusion or positioning, little is known about their involvement in synucleinopathies. In the present study, by studying patients with PD (N = 8), DLB (N = 13), and MSA (N = 5) and controls (N = 16), we explored the involvement of Rubicon family proteins [Rubicon, Pacer and differentially expressed in FDCP8 (DEF8)] in synucleinopathies. Immunohistochemical analysis showed that not only brainstem-type Lewy bodies but also cortical Lewy bodies were immunoreactive for DEF8 in Lewy body diseases, whereas Rubicon and Pacer were detectable in only a few brainstem-type Lewy bodies in PD. Glial cytoplasmic inclusions in patients with MSA were not immunoreactive for Rubicon, Pacer or DEF8. Immunoblotting showed significantly increased protein levels of DEF8 in the substantia nigra and putamen of patients with PD and the temporal cortex of patients with DLB. In addition, the smear band of DEF8 appeared in the insoluble fraction where that of phosphorylated α-synuclein was detected. These findings indicate the involvement of DEF8 in the formation of Lewy bodies. Quantitative and qualitative alterations in DEF8 may reflect the dysregulation of autophagy in Lewy body diseases.

Pathological substrate of memory impairment in multiple system atrophy.

AIMS: Synaptic dysfunction in Parkinson's disease is caused by propagation of pathogenic α-synuclein between neurons. Previously, in multiple system atrophy (MSA), pathologically characterised by ectopic deposition of abnormal α-synuclein predominantly in oligodendrocytes, we demonstrated that the occurrence of memory impairment was associated with the number of α-synuclein-positive neuronal cytoplasmic inclusions (NCIs) in the hippocampus. In the present study, we aimed to investigate how abnormal α-synuclein in the hippocampus can lead to memory impairment. METHODS: We performed pathological and biochemical analyses using a mouse model of adult-onset MSA and human cases (MSA, N = 25; Parkinson's disease, N = 3; Alzheimer's disease, N = 2; normal controls, N = 11). In addition, the MSA model mice were examined behaviourally and physiologically. RESULTS: In the MSA model, inducible human α-synuclein was first expressed in oligodendrocytes and subsequently accumulated in the cytoplasm of excitatory hippocampal neurons (NCI-like structures) and their presynaptic nerve terminals with the development of memory impairment. α-Synuclein oligomers increased simultaneously in the hippocampus of the MSA model. Hippocampal dendritic spines also decreased in number, followed by suppression of long-term potentiation. Consistent with these findings obtained in the MSA model, post-mortem analysis of human MSA brain tissues showed that cases of MSA with memory impairment developed more NCIs in excitatory hippocampal neurons along with α-synuclein oligomers than those without. CONCLUSIONS: Our results provide new insights into the role of α-synuclein oligomers as a possible pathological cause of memory impairment in MSA.

An autopsy case of amyotrophic lateral sclerosis with striatonigral and pallidoluysian degeneration and cat's-eye-shaped neuronal nuclear inclusions.

We report the case of a Japanese woman with sporadic amyotrophic lateral sclerosis (ALS) of 28 months' duration who died at the age of 66 years. Postmortem examination revealed moderate loss of neurons and phosphorylated TDP-43 (p-TDP-43)-immunoreactive neuronal and glial cytoplasmic inclusions in the upper and lower motor neurons. Additionally, marked neuronal loss was observed in the neostriatum, globus pallidum, subthalamic nucleus, and substantia nigra. p-TDP-43-immunoreactive inclusions were frequently found in these areas. Neuronal loss and TDP-43 pathology in the motor, striatonigral, and pallidoluysian systems were predominant on the right side. Moreover, p-TDP-43-immunoreactive cat's-eye-shaped neuronal nuclear inclusions (NNIs) were observed in the affected lesions. NNIs in the striatonigral system were also positive for valosin-containing protein (VCP). We diagnosed the patient as having ALS with striatonigral and pallidoluysian degeneration. Patients with ALS rarely experience pallido-nigro-luysian degeneration. To our best knowledge, only one case of ALS combined with striatonigral and pallidoluysian degeneration has been reported. Neuronal loss in the striatonigral and/or pallidoluysian systems has also been reported in patients with ALS with multisystem degeneration accompanied by long-term use of an artificial respirator. Based on these findings, a possibility of an extremely rare subtype of ALS demonstrating selective loss of neurons in the striatonigral and pallidoluysian systems exists; another possibility is that this type could be an early stage or forme fruste of ALS with multisystem degeneration. Although VCP-positive cat's-eye-shaped NNIs have been reported in spinocerebellar ataxia type-2 cases, our case report presents VCP-positive NNIs in a patient with ALS for the first time.

Neuropathology of Multiple System Atrophy, a Glioneuronal Degenerative Disease.

Multiple system atrophy (MSA) is a fatal disease characterized pathologically by the widespread occurrence of aggregated α-synuclein in the oligodendrocytes referred to as glial cytoplasmic inclusions (GCIs). α-Synuclein aggregates are also found in the oligodendroglial nuclei and neuronal cytoplasm and nuclei. It is uncertain whether the primary source of α-synuclein in GCIs is originated from neurons or oligodendrocytes. Accumulating evidence suggests that there are two degenerative processes in this disease. One possibility is that numerous GCIs are associated with the impairment of oligo-myelin-axon-neuron complex, and the other is that neuronal inclusion pathology is also a primary event from the early stage. Both oligodendrocytes and neurons may be primarily affected in MSA, and the damage of one cell type contributes to the degeneration of the other. Vesicle-mediated transport plays a key role in the nuclear translocation of α-synuclein as well as in the formation of glial and neuronal α-synuclein inclusions. Recent studies have shown that impairment of autophagy can occur along with or as a result of α-synuclein accumulation in the brain of MSA and Lewy body disease. Activated autophagy may be implicated in the therapeutic approach for α-synucleinopathies.

The clinical and neuropathological picture of adult neuronal intranuclear inclusion disease with no radiological abnormality.

In typical adult neuronal intranuclear inclusion disease (NIID) with predilection for the basal ganglia or cerebral cortex, not only neurons but also glial cells harbor intranuclear inclusions. In addition, these inclusions are present in the peripheral autonomic nervous system, visceral organs and skin. In NIID cases with an expansion of GGC repeats in the 5'-untranslated region (5'-UTR) of the Notch 2 N-terminal like C (NOTCH2NLC) gene, these repeats are located in an upstream open reading frame (uN2C) and result in the production of a polyglycine-containing protein called uN2CpolyG. Typically, patients with adult NIID show high-intensity signals at the corticomedullary junction on diffusion-weighted brain magnetic resonance imaging. We report a case of adult NIID in a 78-year-old Japanese male, who suffered from mild, non-progressive tremor during life but showed no radiographic abnormalities suggestive of adult NIID. Pathologically, ubiquitin-, p62- and uN2CpolyG-positive neuronal intranuclear inclusions were particularly frequent in the hippocampal formation, but were also seen in the enteric plexuses, kidney and cardiac muscles. By contrast, glial intranuclear inclusions were barely evident in the affected regions. The present case also had an immunohistochemical profile differing from that of typical adult NIID. The findings in this case suggest that adult NIID can show clinical, radiographic and pathological heterogeneity.

Accumulation of Nonfibrillar TDP-43 in the Rough Endoplasmic Reticulum Is the Early-Stage Pathology in Amyotrophic Lateral Sclerosis.

Transactivation response DNA-binding protein 43 (TDP-43)-immunoreactive neuronal cytoplasmic inclusions (NCIs) are the histopathological hallmarks of amyotrophic lateral sclerosis (ALS). They are classified as skein-like inclusions, round inclusions, dot-like inclusions, linear wisps, and diffuse punctate cytoplasmic staining (DPCS). We hypothesized that TDP-43-immunoreactive DPCS may form the early-stage pathology of ALS. Hence, we investigated phosphorylated TDP-43 pathology in the upper and lower motor neurons of patients with ALS and control participants. We designated patients whose disease duration was ≤1 year as short-duration ALS (n = 7) and those whose duration equaled 3-5 years as standard-duration ALS (n = 6). DPCS and skein-like inclusions were the most common NCIs in short-duration and standard-duration ALS, respectively. The density of DPCS was significantly higher in short-duration ALS than that in standard-duration ALS and was inversely correlated with disease duration. DPCS was not ubiquitinated and disappeared after proteinase K treatment, suggesting that it was not aggregated. Immunoelectron microscopy revealed that DPCS corresponded to nonfibrillar TDP-43 localized to the ribosomes of the rough endoplasmic reticulum (ER). These findings suggest that nonfibrillar TDP-43 accumulation in the rough ER is the earliest TDP-43 pathology in ALS, which may be helpful in developing future TDP-43 breakdown strategies for ALS.

Coronary Artery-Ventricular Pseudoaneurysm Fistula After Myocardial Infarction.

A 56-year-old man presented to the emergency department with chest pain. The diagnosis of acute myocardial infarction caused by a left circumflex artery occlusion was made. After conservative treatment, a fistula between the circumflex artery and the left ventricle, and the evolution of the pseudoaneurysm, were noted. (Level of Difficulty: Advanced.).

Elevated Cystatin-C Levels Are Associated with Increased Mortality in Acute Coronary Syndrome Patients: An HIJ-PROPER Sub-Analysis.

BACKGROUND AND AIMS: We investigated the association between serum cystatin-C (Cys-C) levels and cardiovascular events in patients with acute coronary syndrome (ACS). METHODS: Data of 1,100 patients from the prospective parent study were included. Patients hospitalized for ACS were divided into 4 groups based on quartiles (Q) of Cys-C levels (mg/L) within 24 h of admission: Q1, ≤0.82; Q2, 0.82 < estimated level ≤0.95; Q3, 0.95< estimated level ≤1.12; and Q4, >1.12. The primary endpoint of this study was all-cause mortality, and the secondary endpoint was composite of all-cause mortality, nonfatal myocardial infarction, nonfatal stroke, unstable angina pectoris, or ischemia-driven revascularization. RESULTS: During a median observation period of 4.0 years, the primary endpoint was noted in 5, 12, 18, and 36 patients in Q1-Q4, respectively, with corresponding incidence rates of 1.8%, 4.4%, 6.5%, and 13.5%, respectively (p < 0.0001 for difference among 4 groups). This association persisted even after adjusting for patient characteristics and other laboratory results at baseline (p = 0.04). A stepwise increase in the incidence rate of the secondary endpoint with an incline in Cys-C levels was observed in the nonadjusted model (26.6%, 33.3%, 32.3%, and 39.1% in Q1-Q4, respectively; p = 0.01) but not in the adjusted model (p = 0.3). No difference was observed in the incidence rate of nonfatal myocardial infarction (p = 0.89), nonfatal stroke (p = 0.3), unstable angina pectoris (p = 0.49), and ischemia-driven revascularization (p = 0.47) with an incline in Cys-C levels. CONCLUSION: Elevated Cys-C levels were associated with increased all-cause mortality but not cardiovascular events other than mortality in ACS patients.

Cabergoline, a long-acting dopamine agonist, attenuates L-dopa-induced dyskinesia without L-dopa sparing in a rat model of Parkinson's disease.

Intermittent administration of L-dopa in Parkinson's disease is associated with L-dopa-induced dyskinesia (LID). Long-acting dopamine agonists may reduce the risk of LID by continuous dopaminergic stimulation. We examined the LID-like behavior, preprodynorphin messenger ribonucleic acid (mRNA) expression in the striatum (a neurochemical LID hallmark), and the volume of the entopeduncular nucleus (a pathological LID hallmark) in Parkinson's disease rat models that were treated with L-dopa and cabergoline. Cabergoline co-treatment with L-dopa reduced LID, striatal preprodynorphin mRNA expression, and hypertrophy of the entopeduncular nucleus, indicating that cabergoline has an anti-LID effect independent of the L-dopa-sparing effect.

Simple In-liquid Staining of Microbial Cells for Flow Cytometry Quantification of the Microbial Population in Marine Subseafloor Sediments.

Microbial cell counting provides essential information for the study of cell abundance profiles and biogeochemical interactions with the surrounding environments. However, it often requires labor-intensive and time-consuming processes, particularly for subseafloor sediment samples, in which non-cell particles are abundant. We developed a rapid and straightforward method for staining microbial intracellular DNA by SYBR Green I (SYBR-I) to enumerate cells by flow cytometry (FCM). We initially examined the efficiency of microbial cell staining at various dye/sediment ratios (volume ratio of SYBR-I/sediment [vSYBR/vSed]). Non-cell particles in sediment strongly and preferentially adsorbed SYBR-I dye, resulting in the unsuccessful staining of microbial cells when an insufficient ratio (<1.63 vSYBR/vSed) of SYBR-I dye was present per volume of sediment. SYBR-I dye at an abundance of 10 vSYBR/vSed successfully and stably stained microbial cells in green fluorescence, while the fluorescent color of non-cell particles red-shifted to yellow-orange with the overaccumulation of SYBR-I dye. A low vSYBR/vSed ratio was quickly recognized by a colorless supernatant after centrifugation. At the appropriate vSYBR/vSed ratio, FCM-measured cell concentrations in subseafloor sediments were consistently similar to microscopy counts (>106 cells cm-3). Samples with low cell abundance (<105 cells cm-3) still require cell separation. This modified staining allows us to efficiently process and perform the microbial cell counting of sediment samples to a depth of a few hundred meters below the seafloor with a higher throughput and capability to scale up than procedures employing microscopy-based observations.

Potential oxygen consumption and community composition of sediment bacteria in a seasonally hypoxic enclosed bay.

The dynamics of potential oxygen consumption at the sediment surface in a seasonally hypoxic bay were monitored monthly by applying a tetrazolium dye (2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride [INT]) reduction assay to intact sediment core samples for two consecutive years (2012-2013). Based on the empirically determined correlation between INT reduction (INT-formazan formation) and actual oxygen consumption of sediment samples, we inferred the relative contribution of biological and non-biological (chemical) processes to the potential whole oxygen consumption in the collected sediment samples. It was demonstrated that both potentials consistently increased and reached a maximum during summer hypoxia in each year. For samples collected in 2012, amplicon sequence variants (ASVs) of the bacterial 16S rRNA genes derived from the sediment surface revealed a sharp increase in the relative abundance of sulfate reducing bacteria toward hypoxia. In addition, a notable shift in other bacterial compositions was observed before and after the INT assay incubation. It was Arcobacter (Arcobacteraceae, Campylobacteria), a putative sulfur-oxidizing bacterial genus, that increased markedly during the assay period in the summer samples. These findings have implications not only for members of Delta- and Gammaproteobacteria that are consistently responsible for the consumption of dissolved oxygen (DO) year-round in the sediment, but also for those that might grow rapidly in response to episodic DO supply on the sediment surface during midst of seasonal hypoxia.