Differentiating Brown Tumor From Bone Metastasis in Parathyroid Cancer Using 18 F-FDG PET and 99m Tc-MIBI SPECT.

ABSTRACT: A 69-year-old woman presented with a right clavicle pain. CT revealed a pathological fracture of the right clavicle, multiple osteolytic lesions, and a left cervical mass. 18 F-FDG PET/CT demonstrated a marked FDG uptake in the cervical mass and osteolytic lesions indicative of metastatic parathyroid cancer. 99m Tc-MIBI SPECT/CT revealed either faint or no uptake in the osteolytic lesions. However, a histopathological analysis after a parathyroidectomy and right clavicle biopsy confirmed the diagnosis of parathyroid cancer and the presence of benign brown tumors secondary to hyperparathyroidism. Postoperative imaging showed sclerotic change and a decreased FDG uptake in the bone lesions.

Safety and efficacy of high tracheostomy with inferior retraction of the thyroid isthmus.

OBJECTIVE: In typical surgical tracheostomy, the thyroid isthmus is divided or retracted superiorly and preserved. However, at our institution, the thyroid isthmus is retracted inferiorly and preserved. Thereafter, a tracheal incision is made above the thyroid isthmus. This method, hereinafter defined as high tracheostomy, has the advantage of facilitating immediate access to the trachea in a superficial position; moreover, it can be quickly replaced with cricothyrotomy in emergency situations. However, tracheotomies placed too high can potentially damage the cricoid cartilage, thereby causing subglottic granulation and tracheal stenosis. We aimed to validate the safety and efficacy of high tracheostomy with inferior retraction of the thyroid isthmus. METHODS: This was a retrospective cohort analysis. We analyzed the operative method and other relevant characteristics of 90 patients who underwent surgical tracheostomy between April 2016 and June 2022. For those who underwent high tracheostomies, we analyzed the duration of surgery, amount of intraoperative bleeding, occurrence of complications, problems with stoma closure, and perioperative mortality. RESULTS: High tracheostomy was performed in 73 patients. Subglottic granulation occurred in one patient, and the granulation tissue spontaneously shrank. Subcutaneous emphysema occurred in two patients. No patient developed wound infection or tracheoinnominate artery fistula. Moreover, no patient experienced false route tracheotomy tube insertion because the thyroid glands were located under the stoma. CONCLUSION: The frequency of complications was comparable to that reported in other studies on tracheostomy. Additionally, no patient developed tracheal stenosis secondary to tracheostomy above the thyroid isthmus. Therefore, high tracheostomy with inferior retraction and preservation of the thyroid isthmus is safe and advantageous.

Local recurrence and metachronous multiple cancers after transoral nonrobotic surgery for pharyngeal and laryngeal squamous cell carcinoma: A retrospective multicenter study.

BACKGROUND: Late laryngopharyngeal cancers after transoral surgery include not only local recurrences but also metachronous multiple cancers. METHODS: We compared clinical information, surgical outcomes, and late laryngopharyngeal cancers in patients who underwent transoral nonrobotic surgery for laryngopharyngeal squamous cell carcinoma without lymph node metastases between 2015 and 2021 in a multicenter retrospective study. RESULTS: Four hundred and fifty-seven patients were included. Positive surgical margins were found in 121 patients (26.5%). Twenty-two patients (4.8%) received additional treatment. Positive horizontal margins of invasive carcinoma (p = 0.003) and positive horizontal margins of carcinoma in situ only (p = 0.032) were independent risk factors for local recurrence, and prior radiotherapy (p = 0.001) for metachronous multiple cancers. Local control was significantly worse without additional treatment (p = 0.049), but there was no significant difference in survival. CONCLUSIONS: Patients with positive margins had an increased frequency of local recurrence, but salvage therapy was effective.

Impact of cervical lymph node metastasis on transoral surgery for hypopharyngeal squamous cell carcinoma: A retrospective multicenter study.

BACKGROUND: Hypopharyngeal carcinoma is likely to spread to the lymph nodes, but there is no established strategy for management in transoral surgery. METHODS: We compared oncologic and functional outcomes in a retrospective multicenter study of patients who underwent transoral surgery for hypopharyngeal carcinoma between 2015 and 2021. RESULTS: Two-hundred and thirty-two patients were included. Comparing patients with and without adjuvant radiotherapy, 3-year regional recurrence-free survival (RRFS) was not significantly different in pN2b and pN2c, but was significantly worse in pN3b without adjuvant radiotherapy. In patients without neck dissection, the 3-year RRFS was 85.6%, 76.8%, and 70.0% for T1, T2, and T3 primary lesions, respectively, and was significantly worse for T2 or higher (p = 0.035). CONCLUSIONS: In the absence of extracapsular invasion, regional control did not deteriorate without adjuvant therapy. If prophylactic neck dissection is not performed, careful follow-up is necessary if the primary lesion is T2 or greater.

Complications including dysphagia following transoral non-robotic surgery for pharyngeal and laryngeal squamous cell carcinoma: A retrospective multicenter study.

OBJECTIVE: Transoral surgery is a minimally invasive treatment but may cause severe dysphagia at a lower rate than chemoradiotherapy. METHODS: We compared clinical information, surgical complications, and swallowing function in patients who underwent transoral nonrobotic surgery for laryngo-pharyngeal squamous cell carcinoma between 2015 and 2021 in a multicenter retrospective study. RESULTS: Six hundred and forty patients were included. Postoperative bleeding was observed in 20 cases (3.1%), and the risk factor was advanced T category. Postoperative laryngeal edema was observed in 13 cases (2.0%), and the risk factors were prior radiotherapy, advanced T stage, and concurrent neck dissection in patients with resected HPC. Dysphagia requiring nutritional support was observed in 29 cases (4.5%) at 1 month postoperatively and in 19 cases (3.0%) at 1 year postoperatively, respectively. The risk factors for long-term dysphagia were prior radiotherapy and advanced T category. Short-term risk factors for dysphagia were prior radiotherapy, advanced T category, and concurrent neck dissection, while long-term risk factors for dysphagia were only prior radiotherapy and advanced T category. CONCLUSION: Prior radiotherapy, advanced T stage, and concurrent neck dissection increased the incidence of postoperative laryngeal edema and short-term dysphagia, but concurrent neck dissection did not affect long-term dysphagia. Such features should be considered when considering the indication for transoral surgery and postoperative management.

Immunolocalization of water channel aquaporins in human knee articular cartilage with intact and early degenerative regions.

Aquaporins (AQPs), a family of water channel proteins expressed in various cells and tissues, serve as physiological pathways of water and small solute transport. Articular cartilage is avascular tissue with unique biomechanical structure, a major component of which is "water". Our objective is to investigate the immunolocalization and expression pattern changes of AQPs in articular cartilage with normal and early degenerative regions in the human knee joint, which is the joint most commonly involved in osteoarthritis (OA). Two isoforms (AQPs 1 and 3) of AQPs were examined by immunohistochemical analyses using isoform-specific antibodies with cartilage samples from OA patients undergoing total knee arthroplasty. AQP 1 and AQP 3 were expressed in human knee articular cartilage and were localized in chondrocytes, both in the intact and early degenerative cartilage regions. Compared to the intact cartilage, both AQP 1 and AQP 3 immunopositive cells were observed at the damaged surface area in the degenerative region. These findings suggest that these AQPs play roles in metabolic water regulation in articular cartilage of load bearing joints and that they are responsible for OA onset.

The NPC motif of aquaporin-11, unlike the NPA motif of known aquaporins, is essential for full expression of molecular function.

The recently identified molecule aquaporin-11 (AQP11) has a unique amino acid sequence pattern that includes an Asn-Pro-Cys (NPC) motif, corresponding to the N-terminal Asn-Pro-Ala (NPA) signature motif of conventional AQPs. In this study, we examined the effect of the mutation of the NPC motif on the subcellular localization, oligomerization, and water permeability of AQP11 in transfected mammalian cells. Furthermore, the effect was also assessed using zebrafish. Site-directed mutation at the NPC motif did not affect the subcellular localization of AQP11 but reduced its oligomerization. A cell swelling assay revealed that cells expressing AQP11 with a mutated NPC motif had significantly lower osmotic water permeability than cells expressing wild-type AQP11. Zebrafish deficient in endogenous AQP11 showed a deformity in the tail region at an early stage of development. This phenotype was dramatically rescued by injection of human wild-type AQP11 mRNA, whereas the effect of mRNA for AQP11 with a mutated NPC motif was less marked. Although the NPA motif is known to be important for formation of water-permeable pores by conventional AQPs, our observations suggest that the corresponding NPC motif of AQP11 is essential for full expression of molecular function.

Expression of aquaporin3 in human neoplastic tissues.

AIMS: Aquaporin3 (AQP3) is distributed widely in mammalian tissues and plays an important role in fluid homeostasis. The aim of this study was to investigate the pattern of expression of AQP3 in a variety of human neoplastic tissues and to explore its diagnostic implications. METHODS AND RESULTS: We studied 798 neoplastic tissues using immunohistochemistry with anti-AQP3 antibody. We demonstrated a high positive frequency of AQP3 immunoreactivity in pituitary adenomas, salivary gland tumours, thymic tumours, adenocarcinoma of the lung and prostate, squamous cell carcinomas of the skin, oesophagus and uterine cervix, apocrine carcinoma of the breast, germinal cell tumours of the ovary and testis and urothelial carcinoma of the bladder. None of the sarcomas or central nervous system tumours showed AQP3 immunoreactivity. Most tumours with a high frequency of AQP3 positivity had corresponding or surrounding normal cells that also expressed AQP3. AQP3 was not a specific marker for benign or malignant epithelial neoplasms. CONCLUSION: AQP3 protein is expressed in a variety of epithelial tumours limiting its use as a diagnostic marker. Furthermore, AQP3 expression in tumour cells reflected the expression status of AQP3 in the corresponding normal cells. Our data suggest that water metabolism through AQP3 is maintained during neoplastic transformation in most human tissues.

Close association of aquaporin-2 internalization with caveolin-1.

Aquaporin 2 (AQP2) is a membrane water channel protein that traffics between the intracellular membrane compartment and the plasma membrane in a vasopressin-dependent manner in the renal collecting duct cell to control the amount of water reabsorption. We examined the relation between AQP2 internalization from the plasma membrane and caveolin-1, which is a major protein in membrane microdomain caveolae, in Mardin-Darby canine kidney cells expressing human AQP2 (MDCK-hAQP2 cells). Double-immunofluorescence microscopy showed that AQP2 is colocalized with caveolin-1 in the apical plasma membrane by stimulating the intracellular signaling cascade of vasopressin with forskolin. After washing forskolin, both AQP2 and caveolin-1 were internalized to early endosomes and then separately went back to their individual compartments, which are subapical compartments and the apical membrane, respectively.Double-immunogold electron microscopy in ultrathin cryosections confirmed the colocalization of AQP2 with caveolin-1 at caveolar structures on the apical plasma membrane of forskolin-treated cells and the colocalization within the same intracellular vesicles after washing forskolin. A co-immunoprecipitation experiment showed the close interaction between AQP2 and caveolin-1 in forskolin-treated cells and in cells after washing forskolin. These results suggest that a caveolin-1-dependent and possibly caveolar-dependent pathway is a candidate for AQP2 internalization in MDCK cells.

Immunohistochemical Localization of the Water Channels AQP4 and AQP5 in the Rat Pituitary Gland.

The pituitary gland is composed of the adenohypophysis and neurohypophysis. The adenohypophysis contains endocrine cells, folliculo-stellate (FS) cells, and marginal layer cells, whereas the neurohypophysis mainly comprises axons and pituicytes. To understand the molecular nature of water transfer in the pituitary gland, we examined the immunohistochemical localization of the membrane water channels aquaporin-4 (AQP4) and AQP5 in rat tissue. Double immunofluorescence analysis of AQP4 and S100 protein, a known marker for FS cells, marginal layer cells, and pituicytes, clearly revealed that FS cells and marginal layer cells in the adenohypophysis and the pituicytes in pars nervosa are positive for AQP4. AQP5 was found to be localized at the apical membrane in some marginal layer cells surrounding the Rathke's residual pouch, in which AQP4 was observed to be localized on the basolateral membranes. These results suggest the following possibilities: 1) FS cells especially require water for their functions and 2) transepithelial water transfer could occur between the lumen of Rathke's residual pouch and the interstitial fluid in the adenohypophysis through the AQP4 and AQP5 channels in the marginal layer cells.

Roles of gap junctions in glucose transport from glucose transporter 1-positive to -negative cells in the lateral wall of the rat cochlea.

Despite the importance of glucose metabolism for auditory function, the mechanisms of glucose transport in the cochlea are not completely understood. We hypothesized that gap junctions mediate intercellular glucose transport in the cochlea in cooperation with facilitative glucose transporter 1 (GLUT1). Immunohistochemistry showed that GLUT1 and the tight junction protein occludin were expressed in blood vessels, and GLUT1, the gap junction proteins connexin26 and connexin30, and occludin were also present in strial basal cells in the lateral wall of the rat cochlea. Gap junctions were found among not only these GLUT1-positive strial basal cells but also GLUT1-negative fibrocytes in the spiral ligaments and strial intermediate cells. Glucose imaging using 6-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-6-deoxyglucose (6-NBDG, MW 342) together with Evans Blue Albumin (EBA, MW 68,000) showed that 6-NBDG was rapidly distributed throughout the stria vascularis and spiral ligament, whereas EBA was localized only in the vessels. The gap junctional uncouplers heptanol and carbenoxolone inhibited the distribution of 6-NBDG in the spiral ligament without decreasing the fluorescence of EBA in the blood vessels. These findings suggest that gap junctions mediate glucose transport from GLUT1-positive cells (strial basal cells) to GLUT1-negative cells (fibrocytes in the spiral ligament and strial intermediate cells) in the cochlea.

Immunohistochemical localization of the aquaporins AQP1, AQP3, AQP4, and AQP5 in the mouse respiratory system.

Aquaporins are membrane water channel proteins that function mainly in water transfer across cellular membranes. In our present study, we investigated the immunohistochemical distribution of aquaporin 1 (AQP1), AQP3, AQP4, and AQP5 in the mouse respiratory system by immunofluorescence, immunoperoxidase, and immunoelectron microscopy. AQP3, AQP4, and AQP5 are expressed in epithelial cells, whereas AQP1 is expressed in subepithelial connective tissues and capillaries. In the airway surface epithelia from the nasal cavity to the intrapulmonary bronchioles, AQP5 was found to be mainly localized to the luminal side and both AQP3 and AQP4 to the abluminal side. In the alveolar epithelium, AQP5 is localized to the apical membranes of both type I and type II alveolar cells. Compared with the previous studies on the rat respiratory system, in which AQP5 is restricted to the alveolar type I cells and absent from the airway surface epithelia, we found that AQP5 in the mouse is much more widely distributed throughout the surface epithelia. These results suggest that AQP5 has a critical role in water-handling, such as the maintenance of airway surface liquid and clearance of alveolar fluid in the mouse respiratory system.

Experimental model of lacunar infarction in the gyrencephalic brain of the miniature pig: neurological assessment and histological, immunohistochemical, and physiological evaluation of dynamic corticospinal tract deformation.

BACKGROUND AND PURPOSE: Lacunar infarction accounts for 25% of ischemic strokes, but the pathological characteristics have not been investigated systematically. A new experimental model of lacunar infarction in the miniature pig was developed to investigate the pathophysiological changes in the corticospinal tract from the acute to chronic phases. METHODS: Thirty-five miniature pigs underwent transcranial surgery for permanent anterior choroidal artery occlusion. Animals recovered for 24 hours (n=7), 2 (n=5), 3 (n=2), 4 (n=2), 6 (n=1), 7 (n=7), 8 (n=2), and 9 days (n=1), 2 weeks (n=2), 4 weeks (n=3), and more than 4 weeks (n=3). Neurology, electrophysiology, histology, and MRI were performed. Seven additional miniature pigs underwent transient anterior choroidal artery occlusion to study muscle motor-evoked potentials and evaluate corticospinal tract function during transient anterior choroidal artery occlusion. RESULTS: The protocol had a 91.4% success rate in induction of internal capsule infarction 286+/-153 mm(3) (mean+/-SD). Motor-evoked potentials revealed the presence of penumbral tissue in the internal capsule after 6 to 15 minutes anterior choroidal artery occlusion. Total neurological deficit scores of 15.0 (95% CI, 13.5 to 16.4) and 3.4 (0.3 to 6.4) were recorded for permanent anterior choroidal artery occlusion and sham groups, respectively (P<0.001, maximum score 25) with motor deficit scores of 3.4 (95% CI, 2.9 to 4.0) and 0.0 (CI, 0.0 to 0.0), respectively (P<0.001, maximum score 9). Histology revealed that the internal capsule lesion expands gradually from acute to chronic phases. CONCLUSIONS: This new model of lacunar infarction induces a reproducible infarct in subcortical white matter with a measurable functional deficit and evidence of penumbral tissue acutely.

Immunolocalization of water channel aquaporins in the vomeronasal organ of the rat: expression of AQP4 in neuronal sensory cells.

The vomeronasal organ comprises a pair of narrow tubes in the mammalian nasal septum, serving as a chemosensory system for pheromones. We examined the expression and localization of water channel aquaporins (AQPs) in the rat vomeronasal organ. AQP1 was localized in blood vessels, being particularly abundant in cavernous tissues of the nonsensory mucosa. AQP5 was found in the apical membrane of the gland acinar cells in the vomeronasal organ. AQP3 was detected in the basal cells of the nonsensory epithelium, whereas it was absent in the sensory epithelium. AQP4 was found in both the sensory and the nonsensory epithelia. Interestingly, AQP4 was highly concentrated in the sensory cells of the sensory epithelium. Immunoelectron microscopic examination clearly showed that AQP4 was localized at the plasma membrane in the cell body and lateral membrane of the dendrite, except for the microvillous apical membrane. Nerve fiber bundles emanating from neuronal sensory cells were positive for AQP4, whereby the plasma membrane of each axon was positive for AQP4. These observations clearly show that neuronal sensory cells in the vomeronasal organ are unique in that they express abundant AQP4 at their plasma membrane. This is in marked contrast to the olfactory and central nervous systems, where AQPs are not detectable in neurons, and instead, AQP4 is abundant in the supporting cells and astrocytes surrounding them. The present findings suggest a unique water-handling feature in neuronal sensory cells in the vomeronasal organ.

Disruption of aquaporin-11 produces polycystic kidneys following vacuolization of the proximal tubule.

Aquaporin-11 (AQP11) has been identified with unusual pore-forming NPA (asparagine-proline-alanine) boxes, but its function is unknown. We investigated its potential contribution to the kidney. Immunohistochemistry revealed that AQP11 was localized intracellularly in the proximal tubule. When AQP11 was transfected in CHO-K1 cells, it was localized in intracellular organelles. AQP11-null mice were generated; these mice exhibited vacuolization and cyst formation of the proximal tubule. AQP11-null mice were born normally but died before weaning due to advanced renal failure with polycystic kidneys, in which cysts occupied the whole cortex. Remarkably, cyst epithelia contained vacuoles. These vacuoles were present in the proximal tubules of newborn mice. In 3-week-old mice, these tubules contained multiple cysts. Primary cultured cells of the proximal tubule revealed an endosomal acidification defect in AQP11-null mice. These data demonstrate that AQP11 is essential for the proximal tubular function. AQP11-null mice are a novel model for polycystic kidney diseases and will provide a new mechanism for cystogenesis.

Expression of aquaporin 3 (AQP3) in normal and neoplastic lung tissues.

Aquaporin 3 (AQP3) acts as the membrane channel of water and other small solutes and plays a major role in fluid homeostasis. To investigate the expression of AQP3 in normal and neoplastic lung tissues, we studied a series of 149 lung carcinoma tissues and 2 cell lines by immunohistochemistry, Western blotting, and reverse transcriptase-polymerase chain reaction. In normal lung tissues, immunohistochemical expression of AQP3 was demonstrated in bronchial basal cells, alveolar type II cells, bronchiolar epithelial cells, and secretory cells of submucosal glands. In lung carcinomas, AQP3 expression was observed in 59 (70.2%) of 84 adenocarcinomas. Squamous cell carcinoma and large cell carcinoma had rather low positive ratios (35.8% and 13.4%, respectively). No AQP3 expression was demonstrated in small cell carcinoma, pleomorphic carcinoma, or metastatic colon adenocarcinoma. In adenocarcinomas, AQP3 was detected in all tumors of bronchioloalveolar subtype. Papillary subtype also showed a higher positive ratio of AQP3 compared with that in acinar and solid with mucin subtypes. In addition, AQP3 expression was related to tumor differentiation and clinical stage in adenocarcinomas. Western blotting and reverse transcriptase-polymerase chain reaction analyses confirmed the expression of AQP3 protein and messenger RNA in cell lines and tissues of lung adenocarcinoma. We conclude that AQP3 is widely expressed in the normal respiratory tract and can play an important role in the maintenance of water homeostasis. In addition, lung carcinomas, especially adenocarcinomas, can produce AQP3, possibly in connection with their functional and/or biological nature, although the detailed mechanism of AQP3 expression in lung carcinomas remains to be clarified.

Internalization of caveolae and their relationship with endosomes in cultured human and mouse endothelial cells.

Treatment of cells with pervanadate or vanadate induces the phosphorylation of caveolin-1 and its internalization from the cell surface, but the intracellular fate of caveolae has not been fully elucidated. In the present study, we examined the fate of endocytosed caveolae in human umbilical vein endothelial cells and mouse endothelial KOP2.16 cells. The localization of internalized caveolae and their relationship with the endosomes were examined by immunofluorescence microscopy as well as by immunoprecipitation and chasing of biotinylated transferrin. In untreated cells, caveolin-1 was mostly confined to the cell surface. When cells were treated with either pervanadate for 30 min or vanadate for 3 h, many caveolin-1-labeled vesicles were formed inside the cells, some of which were colocalized with Rab5 or Rab4. The internalized caveolin-1 was colocalized with the endocytosed transferrin in the Rab5-, Rab4- or early endosome antigen-1-labeled compartment where caveolin-1 was phosphorylated. It then moved to the Rabl 1-associated compartment. Immunogold electron microscopy revealed that internalized caveolin-1 colocalized with Rab5 or Rab4 in vesicles larger than caveolae. These results suggest that the internalized caveolae interact with early endosomes.

The Rab27a/granuphilin complex regulates the exocytosis of insulin-containing dense-core granules.

Recently, we identified and characterized a novel protein, granuphilin, whose domain structure is similar to that of the Rab3 effector protein rabphilin3 (J. Wang, T. Takeuchi, H. Yokota, and T. Izumi, J. Biol. Chem. 274:28542-28548, 1999). Screening its possible Rab partner by a yeast two-hybrid system revealed that an amino-terminal zinc-finger domain of granuphilin interacts with Rab27a. Granuphilin preferentially bound to the GTP form of Rab27a. Formation of the Rab27a/granuphilin complex was readily detected in the pancreatic beta cell line MIN6. Moreover, the tissue distributions of Rab27a and granuphilin are remarkably similar: both had significant and specific expression in pancreatic islets and in pituitary tissue, but no expression was noted in the brain. Analyses by immunofluorescence, immunoelectron microscopy, and sucrose density gradient subcellular fractionation showed that Rab27a and granuphilin are localized on the membrane of insulin granules. These findings suggest that granuphilin functions as a Rab27a effector protein in beta cells. Overexpression of wild-type Rab27a and its GTPase-deficient mutant significantly enhanced high K(+)-induced insulin secretion without affecting basal insulin release. Although Rab3a, another exocytotic Rab protein, has some similarities with Rab27a in primary sequence, intracellular distribution, and affinity toward granuphilin, overexpression of Rab3a caused different effects on insulin secretion. These results indicate that Rab27a is involved in the regulated exocytosis of conventional dense-core granules possibly through the interaction with granuphilin, in addition to its recently identified role in lysosome-related organelles.

The distribution and function of aquaporins in the kidney: resolved and unresolved questions.

The membrane water channel aquaporin (AQP) family is composed of 13 isoforms in mammals, eight of which are reportedly expressed in the kidney: AQP1, 2, 3, 4, 6, 7, 8, and 11. These isoforms are differentially expressed along the renal tubules and collecting ducts. AQP1 and 7 are distributed in the proximal tubules, whereas AQP2, 3, and 4 occur in the collecting duct system. They play important roles in the reabsorption of water and some solutes across the plasma membrane. In contrast to other aquaporins found in the kidney, AQP6, 8, and 11 are localized to the cytoplasm rather than to the apical or basolateral membranes. It is therefore doubtful that these isoforms are directly involved in water or solute reabsorption. AQP6 is localized in acid-secreting type A intercalated cells of the collecting duct. AQP8 has been found in the proximal tubule but its cellular location has not yet been defined by immunohistochemistry. AQP11 seems to be localized in the endoplasmic reticulum (ER) of proximal tubule cells. Interestingly, polycystic kidneys develop in AQP11-null mice. Many vacuole-like structures are seen in proximal tubule cells in kidneys of newborn AQP11-null mice. Subsequently, cysts are generated, and most of the mice die within a month due to severe renal failure. Although ER stress and impairment of polycystin-1, the product of the gene mutated in autosomal-dominant polycystic kidney disease, are possible causes of cystogenesis in AQP11-null mice, the exact mechanism of pathogenesis and the physiological function of AQP11 are yet to be resolved.

Gap junctions mediate glucose transport between GLUT1-positive and -negative cells in the spiral limbus of the rat cochlea.

To elucidate the role of the spiral limbus in glucose transport in the cochlea, we analyzed the expression and localization of GLUT1, connexin26, connexin30, and occludin in the spiral limbus of the rat cochlea. GLUT1 and occludin were detected in blood vessels. GLUT1, connexin26, connexin30, and occludin were also expressed in fibrocytes just basal to the supralimbal lining cells. Connexin26 and connexin30 were present among not only these GLUT1-positive fibrocytes but also GLUT1-negative fibrocytes. In vivo glucose imaging using 6-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-6-deoxyglucose (6-NBDG, MW 342) together with Evans Blue Albumin (EBA, MW 68,000) showed that 6-NBDG was rapidly distributed throughout the spiral limbus, whereas EBA was localized only in the vessels. Moreover, the gap junctional uncoupler heptanol inhibited the distribution of 6-NBDG. These findings suggest that gap junctions play an important role in glucose transport in the spiral limbus, i.e., that gap junctions mediate glucose transport from GLUT1-positive fibrocytes to GLUT1-negative fibrocytes in the spiral limbus.