Technological advancements in microelectrode recording have contributed to the field of neurophysiology. Herein, we first review the historical background of the invention of microelectrodes. Next, epoch-making neurophysiological studies using microelectrodes, such as resting potentials, action potentials, inhibitory postsynaptic potentials, and single ion channel currents, are presented. In addition, we describe the molecular mechanisms of synapses involved in memory, mapping of the visual cortex, and functions of place and grid cells for spatial navigation, which were revealed using microelectrodes. We further describe recently developed technologies that combine electrophysiology and molecular biology, including those that contributed to identification of receptor proteins for thermal or mechanical stimuli. When combined with molecular biology, electrophysiology using microelectrodes remains useful.

The distal nephron is the portion of the nephron that extends from the ascending limb of Henle to the collecting duct. This article summarizes some of the physiological functions of the distal nephron, with particular emphasis on the physiological functions of transepithelial transport of sodium, potassium, and chloride. The pathophysiology of the following diseases with dysfunction of the distal nephron is reviewed. (1) Liddle syndrome: a familial disorder with clinical manifestations very similar to primary aldosteronism but with reduced aldosterone secretion. (2) Bartter syndrome/Gitelman syndrome: a group of disorders presenting with renal sodium and potassium wasting. (3) Type II pseudohypoaldosteronism: a group of inherited hypertensive disorders with sodium retention due to the hyperactivity of the newly discovered WNK (with no lysine kinase 4)-NCC (Na⁺-Cl⁻ cotransporter) signaling cascade. Beginning with the identification of the causative genetic abnormalities, rapid progress has been made in understanding the pathogenesis of these diseases at the molecular and cellular levels, resulting in the identification of new regulatory mechanisms of electrolyte transport in the kidney.

Dopaminergic neurons play crucial roles in various physiological functions, such as reward, goal-directed behavior, memory formation, and pain sensation. One of the main dopaminergic cell groups in the brain is located in the retrorubral field (RRF, A8 region). A recent electrophysiological study using rats revealed that distinct neurons within the A8 region respond to the different degrees of the threat and aversive stimuli, and that the RRF is the origin of neural signals for threat and aversive outcomes. However, neurochemical characterization of the constituents of the A8 region is not enough. The aim of this study is to determine the neurochemical characteristics of these A8 neurons. To examine the neurochemical cellular organization of the A8 region, we performed immunohistochemistry for two GABAergic neuronal markers, parvalbumin (PV) and neuronal nitric oxide synthase (nNOS), in relation to tyrosine hydroxylase, a marker of dopaminergic neurons. We observed that the number of PV-positive neurons in the mouse A8 region was lesser than in rats. Moreover, nNOS-positive neurons were not detected within the A8 region in either species. These results indicate that the neurochemical organization of the A8 region was distinct between mice and rats. In addition, the cellular composition of the A8 dopaminergic cell group was distinct from other dopaminergic cell groups, such as the A9 and A10 region, in both mice and rats. Understanding these differences among species and cell groups is worth noting for translating the results obtained with distinct animal models into a clinical application.

We report a case of advanced rectal cancer that could be radically resected after total neoadjuvant therapy (TNT). A 65-year-old man underwent TNT for lower rectal cancer. The patient received a short course of chemoradiation therapy (CRT) at a total dose of 30 Gy to the pelvic area, including lateral lymph nodes, in fractions of 3 Gy administered five times a week over 10 days (days 1-5 and 8-12). The CRT was given in combination with S-1 at a dose of 80 mg twice daily on all days of radiotherapy. After CRT, the patient was scheduled to receive two cycles of S-1 + oxaliplatin (SOX) therapy. SOX was administered over 3 weeks (130 mg/m² oxaliplatin on days 20 and 41, and 80 mg oral S-1 on days 20-33 and 41-54). Robotically-assisted laparoscopic low anterior resection was performed on day 77. Histopathological findings showed only a small amount of residual tumor (residual tumor volume of less than 5%), and the radial margin was negative. There were no severe adverse events, postoperative complications, or functional disorders. These findings demonstrated the effectiveness and safety of TNT with short-term irradiation for rectal cancer. This regimen may be a new candidate for neoadjuvant treatment of previously untreated rectal cancer.

The perivascular space is a normal anatomical structure that forms around perforating arteries and is filled with cerebrospinal fluid. In rare cases, the perivascular space is enlarged and form multiocular cysts measuring 1.5 cm or larger, which are called giant tumefactive perivascular spaces. Seventy-four cases who harbored tumefactive perivascular spaces have been reported to date, and about half of them required CSF diversion. The treatment for multiocular cysts themselves has been reported as being unnecessary. Herein, we report a case of a giant tumefactive perivascular space that caused obstructive hydrocephalus. In the case of obstructive hydrocephalus due to giant tumefactive perivascular spaces, the surgical intervention for the hydrocephalus, such as third ventriculostomy or ventricle-peritoneal shunt, would be the therapeutic choice. Thus, it is crucial to understand the characteristic imaging findings of giant tumefactive perivascular spaces; the signal of the lesions is isointense to the cerebrospinal fluid on each MRI sequence with minimum perifocal edema.

Nasal bleeding can be generally controlled with only intranasal treatment. However, bleeding from large vessels, such as maxillary and internal carotid arteries, is difficult to control only by intranasal treatment, and endovascular treatment is required. Especially nasal bleeding from a ruptured internal carotid artery aneurysm is extremely rare and requires urgent treatment. The patient visited our hospital for sudden nasal bleeding, but the bleeding spontaneously stopped when the patient was first seen. When the blood clot in the natural ostium of the left sphenoid sinus was inhaled at an outpatient situation, massive pulsatile bleeding occurred and continued. The venous route was secured, extracellular fluid was rapidly administered, and tracheal intubation was performed. With computed tomography and angiography examination, the patient was diagnosed with nasal hemorrhage secondary to a ruptured aneurysm in the left internal carotid artery, and the bleeding was controlled by placing endovascular stents and coil in the left internal carotid artery. From the experience of this case, if nasal bleeding occurs around the sphenoidal sinus ostium, clinicians should consider the possibility of nasal bleeding from a ruptured aneurysm of the internal carotid artery and the appropriate treatment should be managed after detailed examinations.

A 73-year-old female underwent a left knee arthroplasty procedure. Postoperative fever persisted and a chest computed tomography (CT) and positron emission tomography (PET) examination was performed, which showed a mass shadow in the right lower lobe of lung and a mass in the left atrium. Based on these findings, we suspected intracardiac extension of the lung tumor or another mass in the left atrium, and surgery was planned. Initially, a right lower lobectomy was performed under a video assisted thoracoscopic surgical procedure. The interlobar plane was separated, then the inferior lobe pulmonary artery was dissected, followed by dissection of the lower trunk of bronchus. A tumor was found on the cranial side of the right inferior pulmonary vein. Next, the chest was opened through a median sternotomy and artificial cardiopulmonary support was started. The tumor was found to be extending from the right inferior pulmonary vein toward the mitral valve and extraction was performed from the left atrium. The entire mass was moved to the right thoracic cavity, then the right lower lobe and mass were removed en bloc. Described herein is a rare case of pulmonary metastasis associated with a renal cell carcinoma extending into the left atrium.

A 57-year-old woman presented with abnormal sensations and muscle weakness in the left upper and lower limbs and difficulty in walking four days after coronavirus disease 2019 (COVID-19) vaccination. The patient had deep sensation deficits and increased tendon reflexes in the left upper and lower limbs. Her head and cervical spinal cord magnetic resonance imaging showed a ring-shaped contrast-enhancing lesion. Cerebrospinal fluid examination showed a mildly elevated cell count, myelin basic protein, and IgG index, and positive oligoclonal bands. The patient was diagnosed as inflammatory demyelinating diseases of the central nervous system (IDDCNS) due to vaccination and was treated with pulse steroids. Her symptoms improved to a greater degree compared to previously reported cases of IDDCNS after COVID-19 vaccination. The disease course of this case was monophasic, but was more similar to multiple sclerosis than to acute disseminated encephalomyelitis (ADEM) according to their diagnostic criteria. Careful long-term observation is necessary because vaccination, as in this case, may lead to relapses in multiple sclerosis (MS) patients who have not received disease-modifying drugs.

The current case report describes the clinical and genetic characteristics of a 16-year-old female proband. She did not have any subjective neurological symptoms preoperatively and who was incidentally diagnosed due to abnormal intraoperative neurophysiological monitoring (IONM) using transcranial electrical stimulation motor evoked potentials (TES-MEP) and somatosensory evoked potentials (SEP) for idiopathic scoliosis, leading to the diagnosis of Charcot-Marie-Tooth disease (CMT) 1B. There was no similar disease in her family history. Nerve conduction velocity testing revealed decreased conduction velocity of the median nerve, and genetic testing indicated myelin protein zero (MPZ) mutation (c242A > G), leading to the diagnosis of demyelinating type CMT1B. The parents had no genetic mutation, and this was a case of de novo mutation. CMT1B is an important differential diagnosis because, similar to our case, there may not be any clinical symptoms. The disease was discovered during a careful evaluation of the patient's scoliosis and other complications. TES-MEP was more useful than SEP for IONM of scoliosis with CMT1B.