Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Digitation junction”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 469 records · Page 26Linked to original sources
PubMed1993

Dentin pretreatment and caries inhibition by a fluoride-releasing resin.

The purpose of this study was to examine the effect that phosphoric acid etchant, used to remove the smear layer, may have on dentin demineralization inhibition. Fifteen molars had Class V preparations placed on the mesial and distal surfaces, the gingival seat being placed 1 mm below the cementoenamel junction. Randomly, one preparation of each tooth had etchant placed carefully on only enamel for 30 seconds. Etchant was placed on the gingival seat dentin of the remaining preparations, as well as the enamel for 30 seconds. A HEMA dentin primer containing maleic acid was placed and allowed to dry on the unetched dentin, then a Bis-GMA resin with tetrabutyl ammonium tetrafluoroborate was placed. Only the fluoridated resin was placed over the dentin that had been etched. All teeth were then restored with resin composite and subjected to an artificial caries challenge (pH 4.4) for 7 days. Sections 100 microns were obtained, photographed under polarized light microscopy and demineralized areas were digitized. Results demonstrated the mean area (mm2 +/- S.D.) demineralization 0.5 mm from the gingival margin to be: etched dentin (0.77 +/- 0.36); non-etched dentin (1.52 +/- 0.98). A t-test indicated that there was significantly less demineralization when the fluoridated resin came in direct contact with dentin that had the smear layer removed (P < 0.05).

Acid Etching, Dental↗
PubMedDate not supplied

A new instrument for continuous recording of the evoked compound electromyogram in the clinical setting.

To study neuromuscular transmission, observation of the evoked compound electromyogram (EMG) has important advantages over observation of the evoked mechanical muscle contraction. Technically, however, recording of the evoked compound EMG, especially in continuous study of several hours duration, has been difficult. Investigators have employed various complicated systems, including tape recording, photorecording, and photographing for such purposes. The authors have applied modern computer technology to construction of an EMG analyzer which enables handling the evoked EMG even more easily than the evoked mechanical contraction. The principle involves digital dissection, storage with memory, readout with time expansion, and analog reconstruction of the compound EMG. The signal can be recorded with ease by use of any suitable hot-stylus or ink-writing oscillographic recorder. Both the waveform and the amplitutde of the EMG can be on-line recorded. The cost compares favorably with comparable devices for similar studies.

Electromyography↗
PubMed2002

Size and shape changes during late fetal growth (137-157 gestational days) in the pigtailed macaque (Macaca nemestrina) craniofacial complex: an application using three-dimensional coordinate data and finite element scaling analysis.

Form changes within the fetal pigtailed macaque (Macaca nemestrina) craniofacial complex was documented using finite element scaling analysis (FESA) and three-dimensional (3D) coordinate data for 35 craniofacial landmarks. Coordinate data were digitized from 3D reconstructions of computed tomography (CT) images and 2D axial slices. Twenty-two fetal pigtailed macaques ranging in age from 137 to 157 gestational days were included (in this species, birth is estimated at 170 gestational days). The null hypothesis that the craniofacial complex grows with isometry during late fetal growth of the craniofacial complex was tested (P < 0.05), and the prediction that morphological change along an anteroposterior axis dominates late fetal growth was also investigated. The null hypothesis was rejected, indicating that allometric growth is present during late fetal growth. Growth along an anteroposterior axis is localized in the palate and mandible. The neurocranium grows along a superoinferior axis, while the neurofacial junction displays growth along both the anteroposterior and superoinferior axes. Mediolateral changes are localized between asterions, the external auditory meati, and maxillary and mandibular alveolar points. Finally, a 3D model of craniofacial growth for this species was created, localizing size and shape changes that occur during late fetal growth for each of the 35 craniofacial landmarks defined in this study.

Animals↗
PubMed1995

Computer-assisted reconstruction of enamel fissures and carious lesions of human premolars.

The origin of cariogenesis in occlusal fissures remains elusive because of limited information about both the fissure structure and the morphologic details of carious lesions occurring there. The present study was aimed at reconstructing the coronal structure of human premolars with the aid of computer-assisted image analysis and, on the basis of the reconstructed structures, investigating the configuration of fissures, their proximity to the enamel-dentin junction (EDJ), and the occurrence and extension of carious lesions around the fissure walls. The coronal portions of the teeth were embedded in polyester resin and then ground off stepwise by hand. Serial images of the enamel contour on successive ground planes were recorded by objective microscopy after it was distinctly demarcated with either 0.5 w/v% carbol fuchsin or 1 w/v% basic fuchsin. Usually, from 150 to 250 photoprints were collected from a single enamel crown to reproduce the details of the fissure structures. The enamel outline (the occlusal and lateral surfaces, fissure walls, and EDJ) and, if present, the outline of caries-attacked areas were traced accurately on those photoprints by means of a digitizing system. The enamel contour data in series were input into an image analyzing system (Nikon COSMOZONE, 2SA). Observation of the computer-drawn coronal enamel allowed us to view the morphologic features of the fissures (shape, divarication, and proximity to EDJ) and to scrutinize the pathway of enamel caries along fissure walls.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Enamel↗
PubMed2006

Werner syndrome and mutations of the WRN and LMNA genes in France.

Werner syndrome (WS) is a pleiotropic disease of premature aging involving short stature, tight, atrophied, and/or ulcerated skin; a characteristic 'birdlike' facies and high, squeaky or hoarse voice; premature greying and thinning of the hair; and early onset cataracts. Additional common symptoms include diabetes mellitus, hypogonadism, osteoporosis, osteosclerosis of the digits, soft tissue calcification, premature atherosclerosis, rare or multiple neoplasms, malformed teeth, and flat feet. Diagnosis can be difficult due to the variable presentation and rarity of the disorder. Transmission is usually autosomal recessive. The WS gene, WRN, is member of the RecQ DNA helicase family. Biallelic mutations of WRN are responsible for most patients. Although heterozygous missense mutations in the LMNA gene have been observed in severely affected WS patients, this only accounts for a small fraction of non-WRN patients. Eighteen WS cases were referred to us for molecular analysis. Eleven had definite and three had probable WS according to the University of Washington Registry clinical criteria. All exons of the WRN gene and their splice junctions were sequenced. Of the fourteen definite or probable cases, 11 had one or more WRN mutation. Thirteen different mutations were found, and ten of these were previously undescribed. There were few phenotypic differences between patients with WRN mutation(s) and those who met clinical criteria though lacking WRN mutations. However, patients with mutations tended to have more symptoms overall, and mutations were not observed in the two cases with cardiomyopathy.

Adult↗
PubMed2003

A flow visualization study of an anatomic coronary artery anastomosis model with an implant.

Flow Streamlining Devices is a new tool in Coronary Artery Bypass Grafting (CABG). They aim in: a) Performing a sutureless anastomosis to reduce thrombosis at the veno-arterial junction, and b) Providing a hemodynamically efficient scaffolding to reduce secondary flow disturbances. Thrombosis and flow disturbances are factors that have been reported as contributing factors to the development of intimal hyperplasia (IH) and failure of the graft. By reducing thrombosis and flow disturbances, it is expected that IH will be inhibited and the lifetime of the graft extended. To evaluate the hemodynamic benefits of such an implant, two models were designed and fabricated. One simulated the geometry of the conventional anastomosis without an implant, and the other simulated an anastomosis with a flow streamlining implant. Identical flow conditions relevant to a coronary anastomosis were imposed on both models and flow visualization was performed with dye injection and a digital camera. Results showed reduction of disturbances in the presence of the implant. This reduction seems to be favorable to hemodynamic streamlining which may create conditions that may inhibit the initialization of IH. However, the compliance and geometric mismatch between the anastomosis and the implant created a disturbance at the rigid compliant wall interface, which should be eliminated prior to clinical applications.

Anastomosis, Surgical↗
PubMed2004

Periodontal repair in dogs: examiner reproducibility in the supraalveolar periodontal defect model.

BACKGROUND: Histometric assessments are routinely used to evaluate biologic events ascertained in histologic sections acquired from animal and human studies. The objective of this study was to evaluate the intra- and inter-examiner reproducibility of histometric assessments in the supraalveolar periodontal defect model. METHODS: Histometric analysis using incandescent and polarized light microscopy, an attached digital camera system, and a PC-based image analysis system including a custom program for the supraalveolar periodontal defect model was performed on histologic sections acquired from one jaw quadrant in each of 12 dogs. The animals had received an experimental protocol including implantation of a coral biomaterial and guided tissue regeneration (GTR) barrier devices, and were evaluated following a 4-week healing interval. Histometric parameters were recorded and repeated within a 3-month interval by two examiners following brief training. Intra- and inter-examiner reproducibility was assessed using the intra-class correlation coefficient (ICC). RESULTS: Most parameters showed high intra-examiner ICCs. Parameters including defect height, connective tissue repair, bone regeneration (height/area), formation of a junctional epithelium, positioning of the GTR device, ankylosis, root resorption, and defect area yielded an ICC> or 0..9. The ICCs for bone density and biomaterial density were somewhat lower (0.8 and 0.7, respectively). The inter-examiner reproducibility was somewhat lower compared to the intra-examiner reproducibility. Nevertheless, the ICCs were generally high (ICC range: 0.6-0.9). CONCLUSIONS: Histometric evaluations in the supraalveolar periodontal defect model yield highly reproducible results, in particular when a single examiner performs the histometric measurements, even when the examiner was exposed to limited training.

Animals↗
PubMed1992

Nervous control of distension-induced relaxation of the porcine lower oesophageal sphincter.

The mechanisms involved in the relaxation of the lower oesophageal sphincter induced by distension of the oesophagus and different parts of the stomach, were studied in an anaesthetized porcine model. A computer technique was developed allowing on-line digitizing of lower oesophageal sphincter (sleeve device) and intragastric pressures. Basal sphincter tone was slightly reduced by truncal vagotomy, an effect which seemed to be reversed by sectioning of the vagosympathetic trunks in the neck. Balloon distension of the body of the oesophagus, relaxed the sphincter irrespective of the denervation procedures carried out. Distension of the whole stomach with increasing amounts of air induced a dose-dependent relaxatory lower oesophageal sphincter response, which was also closely associated with the subsequent increases in intragastric pressure. Denervation procedures did not alter this dose-response relationship. The importance of intramural mechanisms was illustrated by the abolition of distension-induced effects in most animals studied after transection of the gastro-oesophageal junction distal to the sphincter. Balloon distension of the antrum elicited a smaller but significant sphincter relaxation, but the mechanisms behind this response seemed to be more complex than after insufflation of air.

Animals↗
PubMed1990

Noninvasive evaluation of the upper extremity.

Vascular problems of the arm and hand can be assessed by a number of noninvasive modalities that are chosen on the basis of the history and physical examination. For suspected upper-extremity ischemia, we begin with SLPs and velocity-waveform analysis. The former test will define the extent and approximate location of the disease process, and subjective assessment of the waveform will further determine the degree and location of occlusive disease. When digital ischemia is suspected, the Doppler examination combined with intermittent compression of the radial and ulnar arteries is valuable for defining the variable arterial anatomy of the hand and the patency of the common and proper digital arteries. The extent of distal ischemia can be assessed by digital pressures. Duplex scanning has been found to be of value in determining the source of upper-extremity micro-emboli, in imaging suspected aneurysmal changes, and for evaluating arteriovenous fistulae and bypass grafts. Cold testing is used to confirm the diagnosis of Raynaud's disease after excluding proximal occlusive disease. When symptoms suggest intermittent arterial obstruction, arterial compression at the thoracic outlet is assessed by monitoring the arterial waveform during a series of maneuvers that change the anatomy of the outlet. Although a combination of IPG and venous Doppler examination accurately identifies venous occlusion, we routinely use duplex scanning in this setting. In addition to providing both anatomic and hemodynamic information about the subclavian vein, the jugular vein and the junction of the innominate vein can also be studied. Because of its ability to image in a coronal plane, MRI scanning is another nonivasive study that we have found useful for evaluation of venous anatomy and patency of the subclavian, jugular, and innominate veins. Venous thrombosis, often the first manifestation of subclavian vein compression at the thoracic inlet, is best evaluated using duplex scanning.

Arm↗
PubMed1993

Refractoriness of neuromuscular transmission: determination by computer subtraction of neurally evoked compound electromyograms.

Shortly after elicitation of a muscle response by supramaximal stimulation of its motor nerve, there exists a period of refractoriness of neuromuscular transmission when a second stimulation elicits only a submaximal response or no response at all. Many anaesthetics and neuromuscular blocking and facilitatory drugs change the refractoriness of neuromuscular transmission. Measurement of this refractoriness may improve our understanding of the neuromuscular actions of these drugs and be useful in differential diagnosis. However, the neuromuscular refractory periods (RP) are difficult to measure, and the unavailability of normal values renders accurate determination of drug effects impossible. Based on an existing technique of digitization and time expansion of the neurally evoked compound electromyogram (ncEMG), we developed a computer programme of waveform subtraction, and determined in nine normal awake volunteers the various interstimulus intervals when neuromuscular transmission was refractory (RP0), 3/4 refractory (RP.25), half refractory (RP.5), 1/4 refractory (RP.75) or non-refractory (RP1). We confirmed our hypotheses that computer-based waveform subtraction of the digitized ncEMG is a feasible and necessary technique for the accurate determination of the RPs of neuromuscular transmission, and report that the normal values in humans are: RP0 = 1.0 +/- 0.1, RP.25 = 1.3 +/- 0.3, RP.5 = 1.9 +/- 0.3, RP.75 = 2.9 +/- 0.5, and RP1 = 6.6 +/- 1.9 ms (mean +/- SD), respectively, in the ulnar nerve-first dorsal interosseous muscle model.

Adult↗
PubMed2000

Use of fetal fibronectin in women at risk for preterm delivery.

Fetal fibronectin, a large molecular weight glycoprotein produced in the chorion, is expressed in cervical and vaginal secretions in women with disruption of the choriodecidual [table: see text] junction by labor or by inflammation. The presence of FFN in vaginal or cervical secretions before 35 weeks is a moderately good predictor of preterm delivery. The absence of FFN is a strong predictor that preterm delivery is unlikely within the next 7 to 14 days, with NPVs exceeding 99% in some studies. The predictive power of FFN is stronger at earlier gestation ages (24-28 wks) than it is later [table: see text] in pregnancy and is stronger for short-term prediction (7-14 d) than for predicting overall outcome (however, it remains statistically significant for predicting delivery < 37 wks). Although use of FFN in the clinical setting may require some changes to common protocols (e.g., performing sterile speculum examination before digital cervical examination), the use of FFN in patients with suspected preterm labor appears to have significant utility in reducing unnecessary interventions in women with symptoms suggestive of preterm labor. In women without symptoms, the use of FFN may be most beneficial in providing reassurance to some women thought to be at high-risk for preterm delivery because of past obstetric history. Screening women without symptoms at low-risk with FFN is not yet recommended because effective interventions are not demonstrated for patients found to be positive.

Cervix Uteri↗
PubMed1977

Thickness of facial gingiva.

Gingival thickness was measured in 10 subjects with healthy gingiva on the facial aspect of selected maxillary and mandibular teeth at the depth of the gingival sulcus and midway between the sulcus depth and mucogingival line. Measurement instrumentation, consisting of a differential transformer coupled to an oscillator and digital voltmeter was sensitive to the travel of a probe from the gingival surface to tooth surface or alveolar bone. The probe assembly was accurate to 0.01 mm and the average range of differences in replicate measurements under a variety of conditions never exceeded 0.15 mm. 1. Free gingival thickness averaged 1.56 mm + 0.39, attached gingival thickness averaged 1.25 mm + 0.42 and the total mean thickness for all areas measured was 1.41 mm. 2. Thickness in mandibular free and attached gingiva and maxillary free gingiva increased from anterior to posterior. Thickness in maxillary attached gingiva remained fairly constant. 3. Thickness measured at the depth of the sulcus was directly proportional to the free gingival width. 4. Thickness measured midway between sulcus depth and mucogingival junction was inversely proportional to attached gingival width.

Adult↗
PubMed1997

Serotonin-induced intercellular calcium waves in salivary glands of the blowfly Calliphora erythrocephala.

1. Blowfly salivary glands have been used extensively as a model system for the analysis of inositol phosphate-dependent signal transduction. To detect and characterize changes in intracellular free calcium ([Ca2+]i) that might be expected to be triggered by stimulation with serotonin (5-HT), we have carried out digital calcium-imaging experiments on intact glands using the Ca2+-sensitive dye fura-2. 2. 5-HT (1-10 nM) induced repetitive transient increases in [Ca2+]i, i.e. Ca2+ spikes whose frequency was a function of agonist concentration (EC50 = 2.8 nM). 3. Pre-incubation in EGTA decreased the frequency but did not inhibit spiking. Thapsigargin abolished periodic spike activity indicating that the [Ca2+]i rise results from Ca2+ release. Neither caffeine (10 mM) nor ryanodine (10 and 50 microM) induced increases in [Ca2+]i. 4. Oscillatory activity in individual cells was synchronized by regenerative intercellular Ca2+ waves that propagated over distances greater than 400 microm. Colliding waves annihilated each other. 5. Desynchronization of the oscillation pattern by 100 microM 1-octanol suggests the involvement of gap junctions and an intracellular messenger in wave propagation. 6. Local stimulation of glands elicited [Ca2+]i elevations in the stimulated area, but not in adjacent cells, indicating that local increases in [Ca2+]i are not sufficient to trigger Ca2+ waves. However, local stimulation was capable of evoking propagating Ca2+ waves when combined with low-dose 5-HT stimulation of the whole gland. 7. The data are consistent with the hypothesis that: (1) Ca2+ acts as the intercellular messenger and modulates its own release via positive and negative feedback on the inosital 1,4,5-trisphosphate (InsP3) receptor, and (2) sensitization of the InsP3 receptor to Ca2+ by InsP3 is required for the propagation of intercellular Ca2+ waves, as proposed for intracellular Ca2+ waves in Xenopus oocytes.

Animals↗
PubMed1995

Equine pelvic flexure myoelectric activity during fed and fasted states.

The pelvic flexure is the midpoint of the equine large colon that marks the junction of dorsal and ventral components. Previous studies of intraluminal pressure in this region indicate that it could be an important motility control center. The present study was undertaken to expand our knowledge of normal myoelectric activity around the pelvic flexure region. Eight bipolar silver wire electrodes were surgically fixed at 5-cm intervals to the colonic serosa of five adult horses, starting 30 cm oral to the pelvic flexure on the left ventral colon and ending 15 cm aboral to the pelvic flexure on the left dorsal colon (LDC). Recordings of myoelectric activity were done after feed had been withheld for 20 h or when the horses had been allowed to eat hay up to the time of the recording session. The activity was recorded on a polygraph, digitized, processed through a commercial graphics software package, and stored on magnetic tape for later analysis. Action potential activity was basically separated into long spike bursts (LSB) that were > or = 4 s duration and short spike bursts (SSB) that were < 4 s duration and quantified by a software program developed exclusively for the equine large intestine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1976

Computer detection of premature ventricular complexes: a modified approach.

The accuracy of a data reduction system for arrhythmia detection in identifying premature ventricular complexes was evaluated in continuous tape records of 30 patients in a coronary care unit. Computer analysis was performed with a Honeywell 316 digital computer. Threshold values for dominant complexes were automatically determined and recognition of premature ventricular complexes was based on differences in QRS configuration, timing and T wave configuration from the dominant complexes. Verification of the computer accuracy in detecting premature ventricular complexes was made with visual beat by beat inspection using a two channel strip chart recorder with simultaneous recording of the electrocardiogram and computer signal. This procedure allowed for exact beat to beat correlation and, thus, absolute determination of false positive and false negative identification. From 0.5 to 6 continuous hours of monitoring per patient (average 3.5 hours) were analyzed for a total of 105 monitoring hours. The basic cardiac rhythms noted were normal sinus rhythm, sinue arrhythmia, sinus tachycardia, demand pacemaker rhythm, atrial fibrillation and atrioventricular (A-V) dissociation with junctional rhythm. Premature ventricular complexes were evident in 28 tapes (93 percent) including 12 (43% with multifocal premature ventricular complexes and 3 (11 percent) with ventricular tachycardia. The visual count of premature ventricular complexes totaled 7,921. Of these, 7,542 (95 percent) were properly classified by the computer. The total computer count was 8.717, representing a 13 percent false positive and 5 percent false negative identification rate. The false positive identifications of premature ventricular complexes occurred during periods of 10 seconds or more of continuous noise artifact and in the presence of atrial premature complexes conducted aberrantly. When these sections of tape were excluded, the computer had a less than 2 percent false negative and 3 percent false positive rate of identification of premature ventricular complexes.

Arrhythmias, Cardiac↗
PubMed1990

Local accumulation of acetylcholine receptors is neither necessary nor sufficient to induce cluster formation.

Acetylcholine receptors (AChRs) accumulate at developing neuromuscular junctions in part via lateral migration of diffusely expressed receptors. Using a model system--cultured Xenopus muscle cells exposed to electric fields--we have shown that AChRs, concentrated at the cathode-facing cell pole, continue to aggregate there after the field is terminated (Stollberg and Fraser, 1988). These observations are consistent with the possibility that the field-induced increase in receptor concentration triggers the aggregation event. Only 2 other molecular events could initiate the electric field-induced receptor aggregation: (1) a local increase in the density of some other molecules, or (2) a voltage-sensitive mechanism. Treatment of muscle cell cultures with neuraminidase changes the cell surface charge and has been reported to reverse the direction of electromigration for AChRs and concanavalin A binding sites (Orida and Poo, 1978). Using digitally analyzed fluorescence videomicroscopy, we find that AChRs in neuraminidase-treated cultures accumulate at both cell poles in an electric field. After termination of the field, the AChR continues to aggregate at the cathode-facing pole, as in cells not treated with neuraminidase. However, receptor density decreases at the anode-facing pole, indicating that elevated AChR density does not initiate receptor aggregation. Cells pretreated with neuraminidase and trypsin (which blocks receptor aggregation) display reversed receptor distributions compared to untreated controls, indicating that electromigration has indeed been reversed. The rate at which neuraminidase- and trypsin-treated cells approach steady-state distributions indicates a receptor diffusion constant of approximately 1.2 x 10(-9) cm2/sec, consistent with a diffusion trap mechanism of receptor aggregation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Central venous catheter placement for intravenous digital subtraction angiography: an assessment of technical problems and success rate.

Scant attention has been paid to the technical aspects of central venous catheter placement in intravenous digital subtraction angiography (IV-DSA). In a prospective study of 200 unselected patients referred for IV-DSA, technical problems and success rates were recorded. Central venous access via an arm vein was achieved in 95% of patients. In 83% of cases, only one venous puncture was required. The commonest single cause for failure was being unable to find, puncture or introduce a guidewire into a suitable calibre vein at the cubital fossa in the first instance. Once entered with a guidewire, the median cubital/basilic route led to successful catheter passage to the superior vena cava (SVC) on 93% of occasions. The equivalent figure for the cephalic route was 80%. Only two out of 129 attempts at which the cephalic vein was entered failed as a result of being unable to negotiate the cephalic/axillary junction. Venous spasm and branch points in the arm were the main problems when using the cephalic vein and these together were responsible for the differences in success rate between the cephalic and basilic routes. The results indicate that in the clear majority of patients referred for IV-DSA, central venous catheter placement is straightforward. The median cubital/basilic route is preferred but even if the cephalic route has to be used, it should still provide access to the SVC in more than three-quarters of cases. Manoeuvres used to overcome access difficulties are discussed and illustrated.

Adult↗
PubMed2000

[Intra- and intercellular Ca(2+)-signal transduction].

Calcium is one of the most universal signal-transduction elements in a large variety of cells ranging from bacteria to specialized neurons. Ca2+ acts as a second messenger controlling such processes as secretion, cell differentiation or signal transmission. In order to be able to execute their specific functions and to react in a coordinated way to stimuli, multicellular organs need a precise orchestration of cellular functions. For this purpose cells have developed different forms of intercellular communication (IC). In this study we investigated a number of mechanisms of intracellular propagation and IC using experiments with fluorescent Ca(2+)-indicators, confocal microscopy and digital imaging techniques. In ROS 17/2.8 osteoblasts, retinal pigment epithelial cells (RPE) and CPAE endothelial cells, a small mechanical deformation of the plasma membrane results in a transient increase of free cytoplasmic Ca2+ concentration ([Ca2+]i). This Ca(2+)-rise starts at the site of stimulation and propagates concentrically to neighboring cell layers. The intracellular Ca(2+)-wave in RPE and ROS cells is caused by Ca(2+)-influx followed by Ca(2+)-release from the intracellular stores and by intercellular propagation of the Ca(2+)-wave. The [Ca2+]i-transient upon mechanical stimulation of LLC-PK1 epithelial cells, C6 glioma cells and MLO-Y4 osteocytes was limited and/or variable. In CPAE cells only the intracellular release is important for evoking the Ca(2+)-transient, and is followed by IC. IC can occur via gap junctions (GJ) consisting of membrane-spanning proteins, connexins (Cx). It was demonstrated that IC and GJ in RPE and ROS cells can be reversibly blocked by gap-junction inhibitors such as heptanol or halothane. We demonstrated important differences in modulation of gap junctional communication between these cell types. While in RPE cells stimulation of PKC activity was able to inhibit IC, this was not the case in ROS cells. We screened LE-RPE cDNA via PCR using specific primers for different connexins and found no effect of high glucose solutions, which cause decreased intercellular communication, on the Cx-isoforms expressed. Cx43 is the only Cx-isoform present at the protein level for which Western blot analysis revealed the presence of different forms corresponding to different phosphorylated states. Increased phosphorylation of Cx43 was only seen after direct PKC activation by PMA, but not by indirect PKC activation by high glucose levels. The decreased communication by high glucose concentrations was however associated by a decreased expression of cellular Cx43 to about 3/4 of the level in control conditions. High glucose concentrations therefore decrease Cx43 at the protein level via a PKC effect that appears to be independent of the direct activation of PKC by phorbolesters. Mechanical stimulation did not evoke intercellular Ca(2+)-waves in LLC-PK1 epithelial cells, C6 glioma cells and MLO-Y4 osteocytes. In CPAE-endothelial cells, the contribution of gap junctions to IC following mechanical stimulation is negligible, and modulation of gap junctions via phosphorylation or high glucose solutions is absent. Perfusion experiments and pharmacological studies demonstrated that IC following mechanical stimulation of these cells occurs via release of an extracellular mediator. Our experiments provide strong evidence in favor of purinergic agonists as mediators, such as ATP but mainly ADP. In conclusion we can say that cells contain a wide spectrum of mechanisms for intra- and intercellular communication, and that widely different mechanisms can evoke the same phenomenon of intra- and intercellular Ca(2+)-waves.

Animals↗