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PubMedDate not supplied

Respective effects of hindlimb suspension, confinement and spaceflight on myotendinous junction ultrastructure.

This study compares the effects of 14-day confinement and spaceflight with the respective effects of 8, 18 and 29-day hindlimb suspension on rat soleus and plantaris MTJ ultrastructure. Independently of the experimental situation, greater morphological changes were observed in the soleus as compared to the plantaris MTJ. 18 days of suspension and 14 days of confinement resulted in ultrastructural modifications of the digit-like processes in the soleus MTJ. Additional changes were observed in the myofibrils, microtendon and tendon after 29 days of suspension and 4 days of spaceflight. These results emphasize the influence of the intensity and duration of the muscle loading on the MTJ ultrastructure.

Animals↗
PubMed1999

Vaccinia virus intracellular mature virions contain only one lipid membrane.

Vaccinia virus (VV) morphogenesis commences with the formation of lipid crescents that grow into spherical immature virus (IV) and then infectious intracellular mature virus (IMV) particles. Early studies proposed that the lipid crescents were synthesized de novo and matured into IMV particles that contained a single lipid bilayer (S. Dales and E. H. Mosbach, Virology 35:564-583, 1968), but a more recent study reported that the lipid crescent was derived from membranes of the intermediate compartment (IC) and contained a double lipid bilayer (B. Sodiek et al., J. Cell Biol. 121:521-541, 1993). In the present study, we used high-resolution electron microscopy to reinvestigate the structures of the lipid crescents, IV, and IMV particles in order to determine if they contain one or two membranes. Examination of thin sections of Epon-embedded, VV-infected cells by use of a high-angular-tilt series of single sections, serial-section analysis, and high-resolution digital-image analysis detected only a single, 5-nm-thick lipid bilayer in virus crescents, IV, and IMV particles that is covered by a 8-nm-thick protein coat. In contrast, it was possible to discern tightly apposed cellular membranes, each 5 nm thick, in junctions between cells and in the myelin sheath of Schwann cells around neurons. Serial-section analysis and angular tilt analysis of sections detected no continuity between virus lipid crescents or IV particles and cellular membrane cisternae. Moreover, crescents were found to form at sites remote from IC membranes-namely, within the center of virus factories and within the nucleus-demonstrating that crescent formation can occur independently of IC membranes. These data leave unexplained the mechanism of single-membrane formation, but they have important implications with regard to the mechanism of entry of IMV and extracellular enveloped virus into cells; topologically, a one-to-one membrane fusion suffices for delivery of the IMV core into the cytoplasm. Consistent with this, we have demonstrated previously by confocal microscopy that uncoated virus cores within the cytoplasm lack the IMV surface protein D8L, and we show here that intracellular cores lack the surface protein coat and lipid membrane.

Epoxy Resins↗
PubMed2001

Simultaneous arterial calcium dynamics and diameter measurements: application to myoendothelial communication.

The goal of the present study was to analyze the intercellular calcium communication between smooth muscle cells (SMCs) and endothelial cells (ECs) by simultaneously monitoring artery diameter and intracellular calcium concentration in a rat mesenteric arterial segment in vitro under physiological pressure (50 mmHg) and flow (50 microl/min) in a specially developed system. Intracellular calcium was expressed as the fura 2 ratio. The diameter was measured using a digital image acquisition system. Stimulation of SMCs with the alpha(1)-agonist phenylephrine (PE) caused not only an increase in the free intracellular calcium concentration of the SMCs as expected but also in the ECs, suggesting a calcium flux from the SMCs to the ECs. The gap junction uncoupler palmitoleic acid greatly reduced this increase in calcium in the ECs on stimulation of the SMCs with PE. This indicates that the signaling pathway passes through the gap junctions. Similarly, although vasomotion originates in the SMCs, calcium oscillates in both SMCs and ECs during vasomotion, suggesting again a calcium flux from the SMCs to the ECs.

Animals↗
PubMed2001

Effect of H-7 on cultured human trabecular meshwork cells.

PURPOSE: To determine the effect of the serine-threonine kinase inhibitor H-7, which blocks actomyosin contractility and increases outflow facility in live monkeys, on morphology, cytoskeleton, and cellular adhesions of human trabecular meshwork (HTM) cells in culture. METHODS: Cultured HTM cells were videographically recorded and evaluated before and after exposure to H-7 at different concentrations. The subcellular distribution of the actin-based cytoskeleton and associated anchor proteins including vinculin, paxillin, and beta-catenin, as well as phosphotyrosine-containing proteins were evaluated by fluorescence immunocytochemistry and digital fluorescence microscopy. RESULTS: H-7 induced pronounced but reversible HTM cell thickening toward the cell center and deterioration of the actin cytoskeletal network. Cell-extracellular matrix (ECM) and cell-cell adhesions were also affected, but the beta-catenin-rich, vinculin-containing adherens junctions were clearly more resistant than focal contacts. Phosphotyrosine labeling in focal contacts was highly sensitive to H-7. CONCLUSIONS: H-7 induces alterations in cell shape, actin cytoskeleton, and associated focal adhesions in cultured HTM cells, which may be responsible for the effects of H-7 on outflow facility in live monkey eyes.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1998

MDCK cell cultures as an epithelial in vitro model: cytoskeleton and tight junctions as indicators for the definition of age-related stages by confocal microscopy.

PURPOSE: Madin Darby Canine Kidney (MDCK) cells were grown in culture, and age-related morphological changes in the cytoskeleton and tight junction (TJ) network were used to define stages in view of establishing an optimal in vitro model for the epithelial barrier. METHODS: Growth curves and transepithelial electrical resistance (TEER) were determined, and the cytoskeleton (actin, alpha-tubulin, vimentin) and TJ (Zonula occludens proteins ZO1, ZO2) were investigated with immunofluorescent methods by confocal laser scanning microscopy (CLSM) and digital image restoration. RESULTS: TEER measurements indicated that TJ were functional after one day. Values then remained constant. Four morphological stages could be distinguished. Stage I (0-1 day): Sub confluent cultures with flat cells; TJ established after cell-to-cell contacts are made. Stage II (2-6 days): Confluent monolayers with a complete TJ network, which remains intact throughout the later stages. Stage III (7-14 days): Rearrangement in the cytoskeleton; constant cell number; volume and surface area of cells reduced (cobble-stone appearance). Stage IV (> or = 15 days): Dome formation, i.e. thickening and spontaneous uplifting of the cell monolayer. CONCLUSIONS: Based on the structural characteristics of stage III cell cultures, which are closest to the in vivo situation, we expect them to represent an optimal in vitro model to study drug transport and/or interactions with drugs and excipients.

Animals↗
PubMed1996

[Difficulties and complications in transfemoral implantation of stent prostheses in infrarenal abdominal aortic aneurysms].

Between August 31st, 1994 and January 31st 1996, 69 patients received transfemoral application of stentgrafts for treatment of AAA. Only 10 patients received tube grafts in contrast to 59 bifurcated grafts, which were assembled within the aortic lumen. All aneurysms were symptomatic, growing or sacciform. Risk factors seemed to be aggravated in comparison to conventional operations. 59 operations were technically successful, three were converted to open laparotomy, because of technical malfunction twice and misplacement once. 5 postoperative deaths occurred from multiorgan failure. 7 patients were discharged with primary persisting leakage. All patients exhibited reactions to the stentgraft deployment, which mainly referred to the clotting system and/or arterial pressure. Postoperatively nearly all patients presented a "post-implantation syndrome" over days up to 4 weeks. The observed difficulties and complications can be attributed in part to a "learning curve", in part to difficult anatomic situations, which we included in our series. During follow up at 3, 6 and 12 months 7 secondary leakages were observed, three times because of a documented desintegration, once because of suspected beginning desintegration at a stent-graft junction, and three times because of possible failure of graft material. The leakages could be repaired by interventional procedures.

Aged↗
PubMed1999

A missense mutation in connexin26, D66H, causes mutilating keratoderma with sensorineural deafness (Vohwinkel's syndrome) in three unrelated families.

The multiplicity of functions served by intercellular gap junctions is reflected by the variety of phenotypes caused by mutations in the connexins of which they are composed. Mutations in the connexin26 (Cx26) gene ( GJB2 ) at 13q11-q13 are a major cause of autosomal recessive hearing loss (DFNB1), but have also been reported in autosomal dominant deafness (DFNA3). We now report a Cx26 mutation in three families with mutilating keratoderma and deafness [Vohwinkel's syndrome (VS; MIM 124500), as originally described]. VS is characterized by papular and honeycomb keratoderma associated with constrictions of digits leading to autoamputation, distinctive starfish-like acral keratoses and moderate degrees of deafness. In a large British pedigree, we have mapped the defect to the Cx26 locus. All 10 affected members were heterozygous for a non-conservative mutation, D66H, in Cx26. The same mutation was found subsequently in affected individuals from two unrelated Spanish and Italian pedigrees segregating VS, suggesting that D66H in Cx26 is a common mutation in classical VS. This mutation occurs at a highly conserved residue in the first extracellular domain of the Cx26 molecule, and may exert its effects by interfering with assembly into connexons, docking with adjacent cells or gating properties of the gap junction. Our results provide evidence that a specific mutation in Cx26 can impair epidermal differentiation, as well as inner ear function.

Adolescent↗
PubMed2002

Symmetry of bilateral lesions in geographic atrophy in patients with age-related macular degeneration.

BACKGROUND: As a cause for severe visual loss, geographic atrophy of the retinal pigment epithelium is about half as common as choroidal neovascularization in patients with advanced age-related macular degeneration. To assess symmetry, we determined intraindividual variations of various features of bilateral geographic atrophy in patients with atrophic age-related macular degeneration in a cross-sectional study. METHODS: Patients were examined with the use of a confocal scanning laser ophthalmoscope (Heidelberg Retina Angiograph; Heidelberg Engineering, Heidelberg, Germany). Digital infrared reflection images (excitation, 830 nm) and fundus autofluorescence images (excitation, 488 nm) were recorded. The eyes of each patient were compared regarding number, size, and convex hull of the atrophic areas with the use of image analysis software and with respect to fundus autofluorescence changes in the junctional zone. RESULTS: Seventy-two patients (mean +/- SD age, 76.3 +/- 7.9 years) were examined. The number of atrophic areas ranged from 1 to 23 (mean +/- SD, 4.9 +/- 4.6); the size of geographic atrophy, from 0.18 to 30.20 (mean +/- SD, 7.0 +/- 6.6) mm(2); and the size of the convex hull, from 0.18 to 39.20 (mean +/- SD, 11.7 +/- 8.4) mm(2). No statistically significant difference was found when comparing these variables between each left and right eye: number, P =.62; size, P =.81; and convex hull, P =.78. Identical patterns of fundus autofluorescence were observed in 43 (80%) of 54 patients. CONCLUSIONS: There is intraindividual symmetry in eyes with bilateral geographic atrophy in the presence of a wide range of interindividual variability. The findings are in accordance with the view that age-related macular degeneration is not merely the result of a nonspecific aging process. Symmetric manifestations, rather, reflect specific individual determinants in the pathogenesis and manifestation of the disease.

Aged↗
PubMed1985

Morphometric analysis of CNS microvascular endothelium.

The ultrastructural features that are critical to the efficient functioning of the blood-brain barrier (b-bb) were quantified in typical barrier vessels, i.e., cerebral gray and white matter capillaries, and compared with the same parameters in cerebral nonbarrier capillaries (area postrema), and in somatic capillaries, (muscle) of the mouse. The image analysis was done with the help of a simple, rapid system that required only a digitized bit pad and a microcomputer. We found that: (1) The number of pinocytotic vesicles that are thought to be associated with vascular permeability was three times higher in area postrema vessels and nearly seven times higher in muscle vessels than in barrier vessels. (2) A percentage of interendothelial junctions in nonbarrier capillaries displayed areas of separation that may represent interendothelial channels coursing from the luminal to the abluminal surface between areas of tight junctional complexes. Such areas were not observed in barrier capillaries under the normal conditions studied here, but have been seen by others under conditions in which the barrier has been breached. (3) A 39% decrease in wall thickness in barrier capillaries. (4) No differences in mitochondrial density or in area of associated pericytes among capillaries from any region. Therefore we have questioned both the universality of the apparently increased metabolic work capacity of barrier capillaries, and whether pericytes play any role in the barrier under normal conditions.

Animals↗
PubMed2000

Significant increase of aortic root volume and commissural area occurs prior to aortic valve opening.

BACKGROUND AND AIM OF THE STUDY: The increased use of autologous, homologous or heterologous aortic root demands a detailed knowledge of its anatomy and function. The advent of 3-D digital sonomicrometry offered the opportunity to acquire precise information on the root and leaflet movements during the cardiac cycle. METHODS: Under cardiopulmonary bypass, sonomicrometry crystals were implanted in the aortic root and valve of eight sheep. Crystals were sutured at each commissure (n = 3), the top of the sinotubular junction (n = 3), lowest point of the annulus (n = 3), and leaflet tip (n = 3). 3-D coordinates of each crystal were recorded, together with left ventricular and aortic root pressures and ECG. When the animal had returned to a stable hemodynamic condition, the maximum and minimum distances between two crystals, and areas between three crystals, were calculated. Changes in root volume and leaflet position were time-related to the pressure changes. RESULTS: The most significant change between maximum and minimum distance between crystals during the cardiac cycle occurred at the commissural level. Similarly, the triangle defined by the three commissural crystals showed the greatest change in area (47%). The root volume increased by an average of 22%; about 40% of this increase occurred during the isovolumic phase. The aortic leaflets began to open before ejection. CONCLUSION: We postulate that aortic valve opening is initiated by the outward pull of the commissures. These findings should impact on aortic root surgery.

Animals↗
PubMed1998

Dural arteriovenous shunts at the craniocervical junction.

OBJECT: A retrospective analysis was conducted of 10 patients (three women and seven men) who were treated for spinal dural arteriovenous shunts (AVSs) located at the craniocervical junction. This analysis was performed to evaluate the characteristics of this unusual location in contrast with those of the more common thoracic and lumbar AVSs. METHODS: Seven patients presented with subarachnoid hemorrhage (SAH) and one with slowly progressive quadriparesis and dyspnea due to myelopathy. The other two cases were detected incidentally and included a transverse-sigmoid dural AVS and a cerebellar arteriovenous malformation. Angiographic studies revealed that the spinal dural AVSs at the C-1 and/or C-2 levels were fed by the dural branches of the radicular arteries that coursed from the vertebral artery and drained into the medullary veins. Venous drainage was caudally directed in the patient with myelopathy. In contrast, the shunt flow drained mainly into the intracranial venous system in patients with SAH. Furthermore, in four of these patients a varix was found on the draining vein. In all patients, the draining vein was interrupted surgically at the point at which this vessel entered the intradural space, using intraoperative digital subtraction angiography to monitor flow. The postoperative course was uneventful in all patients and no recurrence was confirmed on follow-up angiographic studies obtained in seven patients at 6 months after discharge. CONCLUSIONS: If computerized tomography scanning shows SAH predominantly in the posterior fossa and no abnormalities are found on intracranial four-vessel angiographic study, proximal vertebral angiography should be performed to detect dural AVS at the craniocervical junction. The results of surgical intervention for this disease are quite satisfactory.

Adult↗
PubMed2000

A scalable quantum computer with ions in an array of microtraps

Quantum computers require the storage of quantum information in a set of two-level systems (called qubits), the processing of this information using quantum gates and a means of final readout. So far, only a few systems have been identified as potentially viable quantum computer models--accurate quantum control of the coherent evolution is required in order to realize gate operations, while at the same time decoherence must be avoided. Examples include quantum optical systems (such as those utilizing trapped ions or neutral atoms, cavity quantum electrodynamics and nuclear magnetic resonance) and solid state systems (using nuclear spins, quantum dots and Josephson junctions). The most advanced candidates are the quantum optical and nuclear magnetic resonance systems, and we expect that they will allow quantum computing with about ten qubits within the next few years. This is still far from the numbers required for useful applications: for example, the factorization of a 200-digit number requires about 3,500 qubits, rising to 100,000 if error correction is implemented. Scalability of proposed quantum computer architectures to many qubits is thus of central importance. Here we propose a model for an ion trap quantum computer that combines scalability (a feature usually associated with solid state proposals) with the advantages of quantum optical systems (in particular, quantum control and long decoherence times).

Journal Article↗
PubMed1997

The relationship of bone loss observed on panoramic radiographs with clinical periodontal screening.

The aim of this study was to determine the relationship between bone levels observed on dental panoramic tomographs (DPT) and the WHO/FDI recommended periodontal screening technique: the community periodontal index of treatment needs (CPITN). Computer enhancement and digital analysis were used to improve accuracy and reliability. A total of 199 posterior sextants on DPT radiographs from 50 patients (29 female and 21 male) with a mean age of 42 were examined. A statistically significant relationship was found between CPITN and radiographic measurement from the cemento-enamel junction to the alveolar crestal bone margin (A). The relationship between A and CPITN was found to fit the following equation: square root of A = beta 1 + F, where, F is constant and beta 1 is the coefficient corresponding to the i the codes of CPITN. It was concluded that there was a close correlation between the CPITN screening codes and bone loss as measured on the DPT radiograph.

Adult↗
PubMed1980

Surface morphology of isolated cardiac myocytes from hypertrophied hearts of aging spontaneously hypertensive rats.

Morphologic features of the cell surface were studied in isolated cardiac myocytes obtained from 12 and 48 week old Spontaneously Hypertensive Rats (SHR) and normotensive Wistar-Kyoto (WKY) control rats. Hearts obtained from ether-anesthetized animals were perfused with Ca++-free Hanks' solution containing EGTA and 0.1% collagenase. The hearts were minced and the suspended cells fixed in 2% phosphate buffered glutaraldehyde. Cells mounted on Nuclepore membrane filters were dehydrated in alcohol and critical point dried for SEM. Quantitative evaluation of myocyte length, width and volume was done with a sonic digitizer on H and E stained cells by light microscopy. At both ages studied there was a significant increase in heart weight to body weight ratio, systolic blood pressure and cell size in SHR compared to WKY controls. In the older animals there appeared to be increased numbers of cell junction areas and deep grooves in the cell surface which appeared more pronounced in SHR than in WKY. The cell surface of the myocytes from 48 week old animals had deep capillary grooves surrounded by protruding longitudinal bundles of myofibrils. These changes would result in increased surface area of the larger cells and diminish the effect of increased cell size on diffusion distance from capillary to tissue. These changes in cell morphology were interpreted as providing a protective effect against development of functional impairment in the hypertrophied hearts.

Animals↗
PubMed1975

Extracardiac recordings of His-Purkinje activity during conduction disorders and junctional rhythms.

Previous investigations have demonstrated a surface recording technique using signal averaging to detect electrical activity during the "isoelectric" P-R segment. Various physiological and pharmacological interventions suggest that the source of these potentials isthe His-Purkinje system (HPS). In order to assess the sensitivity of averaged recordings to changes in HPS activation, i.e., conduction defects in the HPS recordings were made directly from the heart surface using a bipolar, anterior-posterior epicardial lead in 15 dogs which underwent thoractomy. The signal was amplified, filtered and averaged using a digital computer for purposes of signal enhancement. The epicardial averaged lead (EAL) contained activity coincident with HPS depolarization and similar to those recorded by leads on the body surface of intact dogs from previous studies. The standard ECG and His bundle electrogram from an electrode catheter served as references in localizing and assessing several conduction disorders experimentally produced by traumatic and ischemic injury. Among the disorders produced were: 1) atrioventricular (A-V) nodal block which resulted in loss of recorded activity in the EAL following the P wave. 2) First and second degree intra-His bundle block produced by anterior septal artery ligation showed split His potentials in the HBE (1 degree) and 2:1 conduction with block in the His bundle (2 degrees). In the blocked beats the EAL showed a reproducible portion of the activity coincident with proximal His bundle activity of the split His potentials in both cases. 3) In four cases of proximal right bundle branch block produced by anterior septal artery ligation the relatively proximal portions of HPS activity in the EAL showed marked diminution. 4) Two cases of distal His bundle or bilateral bundle branch delay were seen as prolonged H-V time and a normal QRS pattern. The early and late portions of the HPS activity in the EAL were not markedly changed while the middle portion was prolonged and fractionated. 5) Junctional rhythms produced by crushing the SA node resulted in no atrial activity occurring prior to HPS depolarization in the EAL. However, the QRS was preceded by HPS activity whose onset was coincident with the H recorded in the His bundle electrogram. The EAL showed consistent and reproducible morphology and timing of HPS activity at different heart rates during normal conduction and consistent alterations of the HPS activity during abnormal conduction.

Animals↗
PubMed2005

Transanal repair of rectocele and full rectal mucosectomy with one circular stapler: a novel surgical technique.

We present a new surgical stapling technique for treatment of rectocele when associated with internal mucosal prolapse or haemorrhoids using only one circular mechanical stapler. Eight female patients, mean age 53 years (range, 42-70), complaining of obstructed defecation with vaginal digitation because of rectocele associated with internal mucosal prolapse underwent transanal repair of rectocele and rectal mucosectomy using one circular stapler between April and July 2004. A running horizontal mattress suture was placed through the base of the rectocele including mucosa, submucosa and the muscle layer of the whole anterior anorectal junction wall. The prolapsed mucosa and the muscular layer were then excised with an electrical scapel. A continuous pursestring rectal mucosa suture was placed 0.5 cm before the previous anterior mucosa and muscle layers resected wound, including the anorectal junction wall which was kept separate from the posterior vaginal wall by a Babcock forceps. Posteriorly, the pursestring suture included only mucosal and submucosal layers. The stapled suture was positioned between normal anterior rectal wall and the anal canal, 0.5 cm above the pectinate line. The stapler was then closed, fired and withdrawn. One patient complained of a perianal hematoma on the seventh postoperative day, requiring surgical excision. Postoperative defecography showed correction of the rectocele and outlet obstruction disappeared in all patients. This novel combined manual-stapled technique for rectocele and rectal internal mucosal prolapse seems to be a safe procedure and the preliminary results are encouraging. Further investigations have to be performed to assess long-term outcome in a larger number of patients.

Adult↗
PubMed2002

Angiogenic effect of fibroblast growth factor-1 and vascular endothelial growth factor and their synergism in a novel in vitro quantitative fibrin-based 3-dimensional angiogenesis system.

BACKGROUND: We have developed an in vitro 3-dimensional angiogenesis system in which the length, distribution, and ultrastructure of induced capillary sprouts were analyzed in response to concentration ranges of fibroblast growth factor (FGF)-1 and vascular endothelial growth factor (VEGF) and synergistic activity quantitated. METHODS: Bovine aorta endothelial cell aggregates were embedded in fibrin gel (FG) supported by a nylon mesh ring. The formed disks were cultured in 24-well plates in assay media. The test growth factors FGF-1, VEGF, or both (0 to 100 ng/mL) with 100 KIU/mL aprotinin were added to the media. The disks (n = 8/group) were digitally photographed and capillary sprouts quantitated. Assay disks were then fixed and sectioned for morphology. RESULTS: In aprotinin-stabilized FG, aggregated ECs invaded FG radially, forming sprouts and capillary networks. Neovessel lumens surrounded by ECs were confirmed on hematoxylin and eosin and transmission electron microscopy and by formation of cell junctions by transmission electron microscopy. The angiogenic effects of FGF-1 and VEGF were dose-dependent in the range from 1 to 100 ng/mL. Significant activity of FGF-1 started at 1 ng/mL and of VEGF at 2 ng/mL. The greatest effect was at the highest concentration (100 ng/mL) for both cytokines. The combination of 10 ng/mL of each FGF-1 and VEGF induced a significantly greater effect than the additive effects of FGF-1 (10 ng/mL) or VEGF (10 ng/mL) alone when analyzed with SAS system for mixed model (P <.0001), and that also exceeded the effects by 20 ng/mL of either FGF-1 or VEGF. CONCLUSIONS: A 3-dimensional capillary network can be induced in aprotinin-stabilized FG using FGF-1 or VEGF with synergism between the 2 angiogens.

Animals↗
PubMed1989

Symplastic Transport of Carboxyfluorescein in Staminal Hairs of Setcreasea purpurea Is Diffusive and Includes Loss to the Vacuole.

The kinetics of symplastic transport in staminal hairs of Setcreasea purpurea was studied. The tip cell of a staminal hair was microinjected with carboxyfluorescein (CF) and the symplastic transport of this CF was videotaped and the digital data analyzed to produce kinetic curves. Using a finite difference equation for diffusion between cells and for loss of dye into the vacuole, kinetic curves were calculated and fitted to the observed data. These curves were matched with data from actual microinjection experiments by adjusting K (the coefficient of intercellular junction diffusion) and L (the coefficient of intracellular loss) until a minimum in the least squares difference between the curves was obtained. (a) Symplastic transport of CF was governed by diffusion through intercellular pores (plasmodesmata) and intracellular loss. Diffusion within the cell cytoplasm was never limiting. (b) Each cell and its plasmodesmata must be considered as its own diffusion system. Therefore, a diffusion coefficient cannot be calculated for an entire chain of cells. (c) The movement through plasmodesmata in either direction was the same since the data are fit by a diffusion equation. (d) Diffusion through the intercellular pores was estimated to be slower than diffusion through similar pores filled with water.

Journal Article↗