Loss of Cdc42 in Exocrine Acini Decreases Saliva Secretion but Increases Tear Secretion-A Potential Model of Exocrine Gland Senescence

Cdc42 is a small GTPase essential for the cell cycle, morphogenesis, and cell adhesion, and it is involved in the polarity of epithelial cells. However, the functional roles of Cdc42 in exocrine glands, such as the maintenance of acini and water secretion, are not yet well understood. In this study, we generated acinar-cell-specific Cdc42 conditional knockout (Cdc42cKO) mice to assess their maintenance of acinar cells and physiological functions in the salivary glands (SGs) and lacrimal glands (LGs). Our data revealed that the loss of Cdc42 altered the luminal structures to bulging structures and induced acinar cell apoptosis in both the parotid glands (PGs) and LGs of Cdc42cKO mice. Interestingly, saliva secretion in response to pilocarpine stimulation was decreased in the Cdc42cKO group, whereas tear secretion was increased. Consistent with the water secretion results, protein expression of the water channel AQP5 in acinar cells was also decreased in the PGs but conversely increased in the LGs. Moreover, the changes that increased AQP5 expression in LGs occurred in the acinar cells rather than the duct cells. The present study demonstrates that Cdc42 is involved in the structural and survival maintenance of acinar cells in SGs and LGs. On the other hand, depletion of Cdc42 caused the opposite physiological phenomena between PGs and LGs.

Spatial and Temporal Coordination of Force-generating Actin-based Modules Drives Membrane Remodeling In Vivo

Membrane remodeling drives a broad spectrum of cellular functions, and it is regulated through mechanical forces exerted on the membrane by cytoplasmic complexes. Here, we investigate how actin filaments dynamically tune their structure to control the active transfer of membranes between cellular compartments with distinct compositions and biophysical properties. Using intravital subcellular microscopy in live rodents we show that: a lattice composed of linear filaments stabilizes the granule membrane after fusion with the plasma membrane; and a network of branched filaments linked to the membranes by Ezrin, a regulator of membrane tension, initiates and drives to completion the integration step. Our results highlight how the actin cytoskeleton tunes its structure to adapt to dynamic changes in the biophysical properties of membranes.

Insertion of circularly permuted cyan fluorescent protein into the ligand-binding domain of inositol 1,4,5-trisphosphate receptor for enhanced FRET upon binding of fluorescent ligand

Binding of fluorescent ligand (FL) to the cyan fluorescent protein (CFP)-coupled ligand-binding domain of the inositol 1,4,5-trisphosphate (IP₃) receptor (CFP-LBP) produces fluorescence (Förster) resonance energy transfer (FRET). A competitive fluorescent ligand assay (CFLA), using the FRET signal from competition between FLs and IP₃, can measure IP₃ concentration. The FRET signal should be enhanced by attaching a FRET donor to an appropriate position. Herein, we inserted five different circularly permuted CFPs in the loop between the second and third α-helices to generate membrane-targeted fluorescent ligand-binding proteins (LBPs). Two such proteins, LBP-cpC157 and LBP-cpC173, localized at the plasma membrane, displayed FRET upon binding the high-affinity ligand fluorescent adenophostin A (F-ADA), and exhibited a decreased fluorescence emission ratio (480 nm / 535 nm) by 1.6- to 1.8-fold that of CFP-LBP. In addition, binding of a fluorescent low-affinity ligand (F-LL) also reduced the fluorescence ratio in a concentration-dependent manner, with EC₅₀ values for LBP-cpC157 and LBP-cpC173 of 34.7 nM and 27.6 nM, respectively. These values are comparable to that with CFP-LBP (29.2 nM), indicating that insertion of cpC157 and cpC173 did not disrupt LBP structure and function. The effect of 100 nM F-LL on the decrease in fluorescence ratio was reversed upon addition of IP₃, indicating binding competition between F-LL and IP₃. We also constructed cytoplasmic fluorescent proteins cyLBP-cpC157 and cyLBP-cpC173, and bound them to DYK beads for imaging analyses. Application of F-ADA decreased the fluorescence ratio of the beads from the periphery to the center over 3 - 5 min. Application of F-LL also decreased the fluorescence ratio of cyLBP-cpC157 and cyLBP-cpC173 by 20-25%, and subsequent addition of IP₃ recovered the fluorescence ratio in a concentration-dependent manner. The EC₅₀ value and Hill coefficient obtained by curve fitting against the IP₃-dependent recovery of fluorescence ratio can be used to estimate the IP₃ concentration.

Cryopreservation of Biologically Functional Submandibular Gland Rudiments from Fetal Mice

BACKGROUND/AIM

Cryopreservation of cell lines has been widely used in the laboratory; however, cryopreservation of organs is still considered to be difficult. The submandibular gland (SMG) of fetal mice is one of the best-characterized organs. We investigated the conditions for cryopreserving SMG rudiments.

MATERIALS AND METHODS

Embryonic day 13 SMG rudiments were cryopreserved with or without a cryoprotectant. They were thawed and incubated in DMEM/F12 medium. Moreover, the influence of EGF stimulation on the signaling cascade after frozen-thawing the rudiments was analyzed by Western blotting.

RESULTS

When SMG rudiments were cryopreserved without a cryoprotectant, all cells in the rudiments died. However, the SMG rudiments that had been preserved in a cryoprotectant showed branching morphogenesis. Additionally, the responsiveness of signaling cascades to EGF did not differ between frozen with a cryoprotectant and non-frozen rudiments.

CONCLUSION

Cryopreservation might be a useful technology for preserving tissues from small organs, such as fetal SMG rudiments.

Transduction of Salivary Gland Acinar Cells with a Novel AAV Vector 44.9

The loss of salivary gland function caused by radiation therapy of the head and neck or autoimmune disease such as Sjögren's syndrome is a serious condition that affects a patient's quality of life. Due to the combined exocrine and endocrine functions of the salivary gland, gene transfer to the salivary glands holds the potential for developing therapies for disorders of the salivary gland and the expression of therapeutic proteins via the exocrine pathway to the mouth, upper gastrointestinal tract, or endocrine pathway, systemically, into the blood. Recent clinical success with viral vector-mediated gene transfer for the treatment of irradiation-induced damage to the salivary glands has highlighted the need for the development of novel vectors with acinar cell tropism able to result in stable long-term transduction. Previous studies with adeno-associated virus (AAV) focused on the submandibular gland and reported mostly ductal cell transduction. In this study, we have screened AAV vectors for acinar cell tropism in the parotid gland utilizing membrane-tomato floxed membrane-GFP transgenic mice to screen CRE recombinase encoding AAV vectors of different clades to rapidly identify capsid isolates able to transduce salivary gland acinar cells. We determined that AAVRh10 and a novel isolate found as a contaminant of a laboratory stock of simian adenovirus SV15, AAV44.9, are both able to transduce parotid and sublingual acinar cells. Persistence and localization of transduction of these AAVs were tested using vectors encoding firefly luciferase, which was detected 6 months after vector administration. Most luciferase expression was localized to the salivary gland compared to that of distal organs. Transduction resulted in robust secretion of recombinant protein in both blood and saliva. Transduction was species specific, with AAVRh10 having stronger transduction activity in rats compared with AAV44.9 or AAV2 but weaker in human primary salivary gland cells. This work demonstrates efficient transduction of parotid acinar cells by AAV that resulted in secretion of recombinant protein in both serum and saliva.

Arginase 1 is involved in lacrimal hyposecretion in male NOD mice, a model of Sjögren's syndrome, regardless of dacryoadenitis status

Key points

Few reports have explored the possibility of involvement of non‐inflammatory factors in lacrimal hyposecretion in Sjögren's syndrome (SS).

RNA‐sequencing analysis revealed that only four genes, including arginase 1, were downregulated in the lacrimal gland of SS model male mice (NOD mice) after onset of lacrimal hyposecretion and dacryoadenitis.

Even in non‐dacryoadenitis‐type NOD mice, tear secretion and arginase 1 expression remained low.

An arginase 1 inhibitor reduced tear secretion and partially reduced saliva secretion in BALB/c mice.

The results indicate that a non‐inflammatory factor, arginase 1, is involved in lacrimal hyposecretion in male NOD mice, regardless of dacryoadenitis status.

Abstract

Lacrimal fluid (tears) is important for preservation of the ocular surface, and thus lacrimal hyposecretion in Sjögren's syndrome (SS) leads to reduced quality of life. However, the cause(s) of lacrimal hyposecretion remains unknown, even though many studies have been conducted from the perspective of inflammation. Here, we hypothesized that a non‐inflammatory factor induces lacrimal hyposecretion in SS pathology, and to elucidate such a factor, we conducted transcriptome analysis of the lacrimal glands in male non‐obese diabetic (NOD) mice as an SS model. The NOD mice showed inflammatory cell infiltration and decreased pilocarpine‐induced tear secretion at and after 6 weeks of age compared to age‐matched BALB/c mice. RNA‐sequencing analysis revealed that only four genes, including arginase 1, were downregulated, whereas many genes relating to inflammation were upregulated, in the lacrimal glands of male NOD mice after onset of lacrimal hyposecretion and dacryoadenitis (lacrimal gland inflammation). Changes in the level of arginase 1 expression were confirmed by real‐time RT‐PCR and western blot analysis. Furthermore, non‐dacryoadenitis‐type NOD mice were used to investigate the relationships among arginase 1 expression, lacrimal hyposecretion and dacryoadenitis. Interestingly, these NOD mice retained the phenotype of dacryoadenitis with regard to tear secretion and arginase 1 expression level. An arginase 1 inhibitor reduced tear secretion and partially reduced saliva secretion in BALB/c mice. In conclusion, a non‐inflammatory factor, arginase 1, is involved in lacrimal hyposecretion in male NOD mice, regardless of dacryoadenitis status. These results shed light on the pathophysiological role of arginase 1 in SS (dry eye).

Few reports have explored the possibility of involvement of non‐inflammatory factors in lacrimal hyposecretion in Sjögren's syndrome (SS).

RNA‐sequencing analysis revealed that only four genes, including arginase 1, were downregulated in the lacrimal gland of SS model male mice (NOD mice) after onset of lacrimal hyposecretion and dacryoadenitis.

Even in non‐dacryoadenitis‐type NOD mice, tear secretion and arginase 1 expression remained low.

An arginase 1 inhibitor reduced tear secretion and partially reduced saliva secretion in BALB/c mice.

The results indicate that a non‐inflammatory factor, arginase 1, is involved in lacrimal hyposecretion in male NOD mice, regardless of dacryoadenitis status.

Cdc42 controls secretory granules morphology in rodent salivary glands in vivo

We previously reported that the small GTPase Cdc42 negatively regulates endocytosis in the salivary gland of live mice. By using intravital subcellular microscopy, we showed that depletion of Cdc42 causes the mis-sorting of plasma membrane components into intracellular vesicles, ultimately leading to the impairment of the homeostasis of the apical plasma membrane. In this study, we report that, besides, Cdc42 depletion alters the ultrastructure of large secretory granules analyzed by transmission electron microscopy. We found that lack of Cdc42 increases the number of granules per cell and alters their structure. Specifically, granules are smaller, less circular and exhibit heterogeneous electron densities in their lumen. Our findings suggest a novel role for Cdc42 in controlling granule biogenesis and/or maturation.

Cdc42 negatively regulates endocytosis during apical membrane maintenance in live animals

Lumen establishment and maintenance are fundamental for tubular organs physiological functions. Most of the studies investigating the mechanisms regulating this process have been carried out in cell cultures or in smaller organisms, whereas little has been done in mammalian model systems in vivo. Here we used the salivary glands of live mice to examine the role of the small GTPase Cdc42 in the regulation of the homeostasis of the intercellular canaliculi, a specialized apical domain of the acinar cells, where protein and fluid secretion occur. Depletion of Cdc42 in adult mice induced a significant expansion of the apical canaliculi, whereas depletion at late embryonic stages resulted in a complete inhibition of their postnatal formation. In addition, intravital subcellular microscopy revealed that reduced levels of Cdc42 affected membrane trafficking from and toward the plasma membrane, highlighting a novel role for Cdc42 in membrane remodeling through the negative regulation of selected endocytic pathways.

Concerted actions of distinct nonmuscle myosin II isoforms drive intracellular membrane remodeling in live animals

Membrane remodeling plays a fundamental role during a variety of biological events. However, the dynamics and the molecular mechanisms regulating this process within cells in mammalian tissues in situ remain largely unknown. In this study, we use intravital subcellular microscopy in live mice to study the role of the actomyosin cytoskeleton in driving the remodeling of membranes of large secretory granules, which are integrated into the plasma membrane during regulated exocytosis. We show that two isoforms of nonmuscle myosin II, NMIIA and NMIIB, control distinct steps of the integration process. Furthermore, we find that F-actin is not essential for the recruitment of NMII to the secretory granules but plays a key role in the assembly and activation of NMII into contractile filaments. Our data support a dual role for the actomyosin cytoskeleton in providing the mechanical forces required to remodel the lipid bilayer and serving as a scaffold to recruit key regulatory molecules.

Imaging membrane remodeling during regulated exocytosis in live mice

In this mini-review we focus on the use of time-lapse light microscopy to study membrane remodeling during protein secretion in live animals. In particular, we highlight how subcellular intravital microscopy has enabled imaging the dynamics of both individual secretory vesicles and the plasma membrane, during different steps in the exocytic process. This powerful approach has provided us with the unique opportunity to unravel the role of the actin cytoskeleton in regulating this process under physiological conditions, and to overcome the shortcomings of more reductionist model systems.

NEVUS CELLS OBSERVED IN THE SEBACEOUS GLANDS

Of sebaceous gland-containing specimens of melanocytic nevi, a total of 79 specimens from 70 cases of nevocellular nevus (consisting of 10 cases of compound nevus and 60 of intradermal nevus), four cases of juvenile melanoma and three of blue nevus were examined light-microscopically in detail for the presence or absence of nevus cells or dermal melanocytes in the sebaceous glands. As a result, clusters of cells that appeared to be nevus cells were found in the sebaceous glands of specimens from a total of three cases, that is, two cases of nevocellular nevus i.e. compound nevus, and one of the cases of juvenile melanoma. Two cases were infantile and one case was the age of puberty. The origin of the nevus cells found in the sebaceous glands is discussed.

Polyethylenimine-mediated expression of transgenes in the acinar cells of rats salivary glands in vivo

Non viral-mediated transfection of plasmid DNA provides a fast and reliable way to express various transgenes in selected cell populations in live animals. Here, we show an improvement of a previously published method that is based on injecting plasmid DNA into the ductal system of the salivary glands in live rats. Specifically, using complexes between plasmid DNA and polyethyleneimine (PEI) we show that the expression of the transgenes is directed selectively to the salivary acinar cells. PEI does not affect the ability of cells to undergo regulated exocytosis, which was one of the main drawbacks of the previous methods. Moreover PEI does not affect the proper localization and targeting of transfected proteins, as shown for the apical plasma membrane water channel aquaporin 5 (AQP5). Overall, this approach, coupled with the use of intravital microscopy, permits to conduct localization and functional studies under physiological conditions, in a rapid, reliable, and affordable fashion.

VAMP4 is required to maintain the ribbon structure of the Golgi apparatus

The Golgi apparatus forms a twisted ribbon-like network in the juxtanuclear region of vertebrate cells. Vesicle-associated membrane protein 4 (VAMP4), a v-SNARE protein expressed exclusively in the vertebrate trans-Golgi network (TGN), plays a role in retrograde trafficking from the early endosome to the TGN, although its precise function within the Golgi apparatus remains unclear. To determine whether VAMP4 plays a functional role in maintaining the structure of the Golgi apparatus, we depleted VAMP4 gene expression using RNA interference technology. Depletion of VAMP4 from HeLa cells led to fragmentation of the Golgi ribbon. These fragments were not uniformly distributed throughout the cytoplasm, but remained in the juxtanuclear area. Electron microscopy and immunohistochemistry showed that in the absence of VAMP4, the length of the Golgi stack was shortened, but Golgi stacking was normal. Anterograde trafficking was not impaired in VAMP4-depleted cells, which contained intact microtubule arrays. Depletion of the cognate SNARE partners of VAMP4, syntaxin 6, syntaxin 16, and Vti1a also disrupted the Golgi ribbon structure. Our findings suggested that the maintenance of Golgi ribbon structure requires normal retrograde trafficking from the early endosome to the TGN, which is likely to be mediated by the formation of VAMP4-containing SNARE complexes.

Gravity loading induces adenosine triphosphate release and phosphorylation of extracellular signal-regulated kinases in human periodontal ligament cells

AIM

The periodontal ligament (PDL) receives mechanical stress (MS) from dental occlusion or orthodontic tooth movement. Mechanical stress is thought to be a trigger for remodeling of the PDL and alveolar bone, although its signaling mechanism is still unclear. So we investigated the effect of MS on adenosine triphosphate (ATP) release and extracellular signal-regulated kinases (ERK) phosphorylation in PDL cells.

METHODS

Mechanical stress was applied to human PDL cells as centrifugation-mediated gravity loading. Apyrase, Ca(2+)-free medium and purinergic receptor agonists and antagonists were utilized to analyze the contribution of purinergic receptors to ERK phosphorylation.

RESULTS

Gravity loading and ATP increased ERK phosphorylation by 5 and 2.5 times, respectively. Gravity loading induced ATP release from PDL cells by tenfold. Apyrase and suramin diminished ERK phosphorylation induced by both gravity loading and ATP. Under Ca(2+)-free conditions the phosphorylation by gravity loading was partially decreased, whereas ATP-induced phosphorylation was unaffected. Receptors P2Y4 and P2Y6 were prominently expressed in the PDL cells.

CONCLUSION

Gravity loading induced ATP release and ERK phosphorylation in PDL fibroblasts, and ATP signaling via P2Y receptors was partially involved in this phosphorylation, which in turn would enhance gene expression for the remodeling of PDL tissue during orthodontic tooth movement.

Isoproterenol stimulates transient SNAP23-VAMP2 interaction in rat parotid glands

The exocytosis of salivary proteins is mainly regulated by cAMP, although soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), which mediate cAMP-dependent exocytic membrane fusion, have remained unidentified. Here we examined the effect of isoproterenol (ISO) and cytochalasin D (CyD) on the level of SNARE complexes in rat parotid glands. When SNARE complexes were immunoprecipitated by anti-SNAP23, the coprecipitation of VAMP2 was significantly increased in response to ISO and/or CyD, although the coprecipitation of VAMP8 or syntaxin 4 was scarcely augmented. These results suggest that the SNAP23-VAMP2 interaction plays a key role in cAMP-mediated exocytosis from parotid glands.

Spontaneous Ca2+ oscillations via purinergic receptors elicit transient cell swelling in rat parotid ducts

Rat parotid ductal cells were found to exhibit spontaneous Ca(2+) oscillations. These oscillatory Ca(2+) responses were observed during continuous perfusion with physiological salt solution at 37 degrees C in the absence of calcium mobilizing agonist stimulation. These Ca(2+) oscillations were completely blocked by the purinergic receptor inhibitors, pyridoxal phosphate-6-azo (benzene-2,4-disulfonic acid) (PPADS) and suramin, but were not blocked by the muscarinic antagonist, atropine, nor the alpha-adrenergic antagonist, phentolamine. Simultaneous observation with fura-2 fluorescence and differential interference contrast (DIC) images showed that the spontaneous elevations of [Ca(2+)]i were well correlated with the shape changes of the ductal cells. Using a plasma membrane fluorescence probe, we found that the changes in DIC images reflected spontaneous cell swelling of ductal cells. Electron microscopic analysis after Ca(2+) imaging indicated that the spontaneously oscillating duct cells contained numerous granules at the luminal side, which is characteristic of the granular duct cells. These results indicate that the spontaneous [Ca(2+)]i increase occurs through purinergic receptors, and activates Ca(2+)-dependent ion transporters and/or channels. Our findings present the possibility that spontaneous Ca(2+) oscillations via purinergic receptors are involved in the regulation of the electrolyte composition of saliva in resting states.

Spontaneous oscillations in intracellular Ca(2+) concentration via purinergic receptors elicit transient cell swelling in rat parotid ducts

Using multiphoton microscopy, we established that rat parotid ductal cells exhibit spontaneous oscillations in intracellular Ca(2+) concentration ([Ca(2+)](i)). These oscillatory Ca(2+) responses were observed during continuous perfusion with a physiological salt solution at 37 degrees C in the absence of calcium mobilizing agonist stimulation. The timing and patterns of these spontaneous Ca(2+) oscillations varied among individual ductal cells, and the average number of Ca(2+) responses in a single responding ductal cell was 2.1 in a 10-min recording period. High-speed scanning (0.6 s/image) revealed that most spontaneous elevations in [Ca(2+)](i) were initiated at the luminal side of ductal cells and spread toward the basal side within 2 s. Electron microscopic analysis after Ca(2+) imaging indicated that spontaneously oscillating ducts contained numerous granules at the luminal side, which is characteristic of granular ducts. These Ca(2+) oscillations were completely blocked by the purinergic receptor inhibitors 4-[[4-formyl-5-hydroxy-6-methyl-3-[(phosphonooxy)methyl]-2-pyridinyl]azo]-1,3-benzenedisulfonic acid (PPADS) and suramin but were not blocked by the muscarinic antagonist atropine or the alpha-adrenergic antagonist phentolamine. Simultaneous observation of fura-2 fluorescence and differential interference contrast (DIC) images showed that spontaneous elevations of [Ca(2+)](i) were well correlated with changes in shape of ductal cells. Using a plasma membrane fluorescence probe, SynaptoGreen C4, we found that the changes in DIC images reflected spontaneous cell swelling of ductal cells. Our findings present the possibility that purinergic receptors mediate spontaneous Ca(2+) oscillations in parotid ductal cells and regulate electrolyte reabsorption from the primary saliva in the resting state.

Use of Fluorescence Resonance Energy Transfer-based Biosensors for the Quantitative Analysis of Inositol 1,4,5-Trisphosphate Dynamics in Calcium Oscillations

Inositol 1,4,5-trisphosphate (IP(3)) is an intracellular messenger that elicits a wide range of spatial and temporal Ca(2+) signals, and this signaling versatility is exploited to regulate diverse cellular responses. In this study, we have developed a series of IP(3) biosensors that exhibit strong pH stability and varying affinities for IP(3), as well as a method for the quantitative measurement of cytosolic concentrations of IP(3) ([IP(3)](i)) in single living cells. We applied this method to elucidate IP(3) dynamics during agonist-induced Ca(2+) oscillations, and we demonstrated cell type-dependent differences in IP(3) dynamics, a nonfluctuating rise in [IP(3)](i) and repetitive IP(3) spikes during Ca(2+) oscillations in COS-7 cells and HSY-EA1 cells, respectively. The size of the IP(3) spikes in HSY-EA1 cells varied from 10 to 100 nm, and the [IP(3)](i) spike peak was preceded by a Ca(2+) spike peak. These results suggest that repetitive IP(3) spikes in HSY-EA1 cells are passive reflections of Ca(2+) oscillations, and are unlikely to be essential for driving Ca(2+) oscillations. In addition, the interspike periods of Ca(2+) oscillations that occurred during the slow rise in [IP(3)](i) were not shortened by the rise in [IP(3)](i), indicating that IP(3)-dependent and -independent mechanisms may regulate the frequency of Ca(2+) oscillations. The novel method described herein as well as the quantitative information obtained by using this method should provide a valuable and sound basis for future studies on the spatial and temporal regulations of IP(3) and Ca(2+).

Multi-photon microscopic imaging of rat parotid ducts demonstrates cellular heterogeneity in Ca2+ responsiveness

The heterogeneity of salivary ductal cells, with regard to their sensitivity to Ca(2+)-mobilizing agonists, was visualized by multi-photon microscopy. Stimulation of isolated parotid ducts with 0.1 and 1 microM epinephrine (Epi) elevated the intracellular Ca(2+) levels ([Ca(2+)](i)) in approximately 30% and >90% of the ductal cells, respectively. Of the 0.1 microM Epi-responsive cells, 80% responded rapidly to subsequent stimulation with 1 microM Epi. Similarly, threshold concentrations (0.5 or 1 microM) of phenylephrine (PhL), carbachol (CCh) or ATP, induced responses in approximately 20% of the ductal cells, and subsequent stimulations with 10 microM of the same agonist activated approximately 80% of ductal cells. These observations indicate that parotid ducts contain a certain subpopulation of cells, which exhibits particularly high sensitivity to these Ca(2+)-mobilizing agonists, compared to the remaining ductal cells. Sequential stimulation with threshold concentrations of PhL, CCh, and ATP induced Ca(2+) responses in approximately 33% of ductal cells. Of these responsive cells, the majority (69%) could only respond to one of the three agonists; while a small minority (9%) were capable of responding to all three agonists. These results indicate that low concentrations of PhL, CCh, and ATP activate different subpopulations of parotid ductal cells.

A novel fluorescent method employing the FRET-based biosensor "LIBRA" for the identification of ligands of the inositol 1,4,5-trisphosphate receptors

LIBRA is a fluorescent biosensor of inositol 1,4,5-trisphosphate (IP(3)) and is composed of the ligand-binding domain of the rat type 3 IP(3) receptor and cyan and yellow fluorescent proteins. We examined the responses of LIBRA and its IP(3)-insensitive mutant LIBRA-N to compounds known to inhibit IP(3)-induced Ca(2+) release. Heparin, a competitive antagonist of IP(3) receptors, increased the emission ratio of LIBRA but not that of LIBRA-N. In contrast, 2-aminoethoxydiphenyl borate, a known non-competitive inhibitor of IP(3) receptor, decreased the emission ratios of both LIBRA and LIBRA-N. Thus, the concurrent use of LIBRA-N with LIBRA identifies nonspecific responses. These results indicate that LIBRA and its mutant control can be used to detect specific agonists and antagonists of IP(3) receptors. We also demonstrate the utility of LIBRA and LIBRA-N in discriminating between specific and nonspecific responses in intact cells.

Differential Ca2+responses induced by thrombin and thrombin-receptor agonist peptides in HSY-EA1 cells

We examined the mechanism by which protease-activated receptor (PAR)-1 is desensitized by comparing the effect of thrombin and the soluble agonist peptide SFLLRN on Ca(2+)responses in HSY-EA1 cells. Thrombin-induced increases in cytosolic Ca(2+)concentrations ([Ca(2+)](i)) returned to basal levels within 60 s, but SFLLRN generated a sustained [Ca(2+)](i)elevation. Interestingly, thrombin-desensitized cells partially retained their ability to respond to SFLLRN. We desensitized PAR-2 by pretreating cells with SLIGKV to confirm that this response was not due to PAR-2, which can recognize SFLLRN. The highly specific PAR-1 agonist peptide TFLLR also increased [Ca(2+)](i)in PAR-2-desensitized cells pretreated with thrombin. These observations indicate that thrombin disarms PAR-1 from further proteolytic activation, but leaves the receptor responsive for non-tethered ligands.

[Three-dimensional analysis of eye movements induced by roll and pitch tilt]

The torsional eye movements induced by the right and left ear-down position are known as "ocular counter-rolling" but the mechanism of the horizontal and vertical eye movements has not been clarified. The vertical eye movements induced by backward tilt are known as the "doll reflex", but clear eye movements are induced by forward tilt. The mechanism of horizontal and torsional eye movements are unclear. To detect 3D eye movements in the roll and pitch planes, we performed 3D analysis of eye movements by our video-oculographic method. During roll tilt, counter-torsional eye movements were clearly induced, but no definite, eye movements were observed in the horizontal and vertical components of eye movements. During pitch tilt, downward eye movements were observed following backward tilt, but no clear eye movements were observed following forward tilt. Moreover, no clear horizontal or torsional eye movements were observed during pitch tilt. These results suggest that the response to pitch tilt depends on the saccular input.

Three dimensional eye movement analysis during off vertical axis rotation in human subjects

Three dimensional analysis of eye movements during OVAR was performed in 37 healthy human subjects using the computerized image recognition technique developed by us. The modulation component of eye movement was observed in all three components (horizontal, vertical and torsional), whereas the bias component was only clearly seen in the horizontal eye movement. The phase lag of the torsional component was quite consistent with a small variation between each subject with respect to the head position. The phase of vertical eye movement was, however, less consistent compared to that of the horizontal and torsional eye movements. From these results, in human subjects, there should be some differences in the dynamic function of the otolith system compared to that observed in monkeys.

Three-dimensional analysis of pressure nystagmus in labyrinthine fistulae

In this study we analysed pressure nystagmus three-dimensionally in subjects with labyrinthine fistulae. The fistulae were localized in the lateral canal in five patients, in the posterior canal in one patient and in both lateral and anterior canals in two patients. The eye velocities during the fistula test in patients with lateral canal fistula and in a patient with posterior canal fistula were closely aligned with the anatomical axes. On the other hand, pressure nystagmus in cases with fistulae of both the lateral and anterior canals were not aligned with the anatomical axes of the combination of both canals.

Effects of fasting on distribution and excretion of lead following long-term lead exposure in rats

Lead was given to rats through drinking water containing 100 ppm lead acetate for 20 days. Delta-aminolevulinic acid dehydratase (ALAD) activity in erythrocytes was significantly lower (p < 0.05) at 20 days after Pb treatment. Erythrocytic ALAD activity was significantly lower (p < 0.05) in fasted rats than in fed rats with or without Pb pretreatment. Serum glutamic pyruvic transaminase and glutamic oxaloacetic transaminase activities after 6 days of fasting were significantly higher (p < 0.05) in Pb pretreated rats than in other groups (Pb nontreated fed and fasted rats, and Pb pretreated fed rats). Long periods of fasting strongly enhanced these serum-enzymes elevations induced by lead. Maximum Pb concentrations and total amount in feces increased in rats fasted for 3 days regardless of Pb pretreatment. On the other hand, total amount of Pb in feces of rats fasted for 6 days were not significantly different from the other groups because their fecal volume decreased to about 1% of fed rats. The Pb concentrations of liver, kidney, spleen, and femur increased significantly in Pb pretreated rats compared to in controls, but there were no significant differences between the fed and fasted rats.

4'-galactooligosaccharide affects sodium and potassium metabolism in rats

The effect of different levels (0, 10 and 20%) of O-beta-D-galactopyranosyl-(1-4)-O-beta-D-galactopyranosyl-(1-4)-D- glucose (4'-GL) on the bioavailability of sodium and potassium was studied in 18 male rats. Three 3-d metabolic balance studies were conducted during the 62-d feeding trial. These were between d 30 and 32 (first period), 45 and 47 (second period) and 60 and 62 (third period). Growth and food intake were not significantly different (P less than 0.05) between the control group and the 4'-GL-fed groups. In rats fed 10 and 20% 4'-GL diet, the fecal sodium excretion was significantly greater (P less than 0.05) in all three balance periods. Fecal potassium excretion was significantly greater (P less than 0.05) in the 10% 4'-GL-fed group in the second balance period and the 20% 4'-GL-fed group in all balance periods relative to the control group. Although not statistically significant, rats in the 4'-GL-fed groups exhibited a tendency for lower sodium retention and higher potassium retention compared with the control group. The cecal weight of rats in both 4'-GL-fed groups was significantly heavier (P less than 0.05) than that of the control group at the end of study. Sodium concentration in the cecum was significantly lower (P less than 0.05) in the 20% 4'-GL-fed group relative to the other groups.

Merkel cell tumor

A Merkel cell tumor appeared on the left cheek of an 83-year-old female was reported. The tumor was located mainly in the dermis and infiltrated to the subcutaneous adipose tissue with an involvement of the blood vessels and lymphatics at the periphery. Electron-microscopically, few of the dense-cored granules and the single globular aggregates of intermediate filaments at the nuclear indentations were observed. Electron-microscopic uranaffin reaction proved positive reaction on the dense-cored granules. Half of the cytoplasmic border was smooth, while the rest had short projections. Desmosomes or junctional complexes were not detected among the tumor cells. Immunohistochemically, the cytoplasm of tumor cell showed positive reaction to both neuron-specific enolase (NSE) and keratin. The single globular positive spots of the latter were localized in accordance with the aggregates of intermediate filaments. These findings suggested a neurogenic origin with double differentiation, epithelial and neuroendocrine, of the Merkel cell tumor.

A T cell leukemia line produces factor(s) that render rat neutrophils cytotoxic

Proteose-peptone-induced intraperitoneal neutrophils from rats were activated in terms of tumor cytotoxicity by pretreatment with culture supernatants from a human T cell leukemia line, Jurkat (culture sup). Culture sup-treated neutrophils showed cytotoxicity against various tumor cell lines. The cytotoxicity of culture sup-treated neutrophils was dependent on the number of neutrophils and the concentration of culture sup. Cytostasis by activated neutrophils was observed very early in the assay incubation period (within 6 hr), but cytolysis first occurred at 24 hr after the start of incubation. Factor(s) in culture sup responsible for the activation of cytotoxic neutrophils were stable to temperature and pH treatments, and their molecular weight was higher than 10,000. The responsible factor(s) for activation of cytotoxic neutrophils were different from interleukin-2, serum-derived factor, and bacterial lipopolysaccharide.