Structures of Physiological Interest in the Frog Heart Ventricle

Two structures of physiological interest in frog heart ventricles have been examined in detail: (a) the layer of endothelial cells which encloses each bundle of heart fibres, and (b) the sarcoplasmic reticulum (SR) inside the heart fibres. Some additional observations on fibre sizes and types have been made. Movement across the endothelial cell layer of molecules (molecular or ionic size ≤ 12.5 nm) occurs through narrow clefts separating each endothelial cell from its neighbour. This conclusion results from experiments made with the extracellular markers ferritin and horseradish peroxidase. A diffusion equation describing the movement of solutes into and out of the fibre bundle has been derived using several geometrical parameters, such as the length and width of the clefts and the size of the extracellular aqueous space inside the bundle, all of which were determined from electron micrographs of the tissue. The theoretical solution for a stepwise change of external calcium concentration gives a halftime of 2.3 s (± 0.8 s, S.D. of 13 bundles) for diffusion equilibrium at the surface of the heart fibres; this value, however, is likely to be an overestimate, by some 20-30 %, on account of several systematic errors which are described. The sarcoplasmic reticulum in heart fibres consists of a network of thin tubules which partially encircle the myofibrils at Z-line level and also form occasional longitudinal connexions. Branches extend to peripheral regions of the cell and terminate in close apposition to the inner surface of the cell membrane. The volume of the SR is estimated to be approximately 0.5% of the myofibrillar volume of the cells. Cross-sectional areas of heart fibres (and also their shapes) vary considerably, from less than 2 to more than 100 µm2 (average 17.4 µm2).Fibres of large size and small surface/volume ratio contain many fewer myofibrils and more glycogen granules than fibres of the same size but larger surface/volume ratio. Physiological implications of these results are discussed.

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Myopia, corneal endothelial cell density and morphology in a Japanese population-based cross-sectional study: the JPHC-NEXT Eye Study

Scientific Reports ◽

10.1038/s41598-021-85617-4 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Naohiko Aketa ◽

Miki Uchino ◽

Motoko Kawashima ◽

Yuichi Uchino ◽

Kenya Yuki ◽

...

Keyword(s):

Endothelial Cell ◽

Cell Density ◽

Contact Lenses ◽

Population Based ◽

Cross Sectional Study ◽

Corneal Endothelial Cell ◽

Endothelial Cell Density ◽

Sectional Study ◽

Cross Sectional ◽

Corneal Endothelial Cell Density

AbstractThis population-based cross-sectional study was performed to determine the mean corneal endothelial cell density (ECD), coefficient of variation (CV), and hexagonality (HEX), and their associations with myopia in Japanese adults living in Chikusei city. Of 7109 participants with available data, 5713 (2331 male and 3382 female) participants were eligible for analysis. After assessing the relationship between participant characteristics and spherical equivalent refraction (SER), the association of SER with the abnormal value of ECD (< 2000 cells/mm), CV (≥ 0.40), and HEX (≤ 50%) were determined using the logistic regression models adjusting for potential confounders (age, intraocular pressure, keratometric power, height, and antihypertensive drug use). In male participants, there was no statistically significant relationships between SER and endothelial parameters. In female participants, compared to emmetropia, SER ≤ − 6 D had significantly higher odds ratio (OR) of having the abnormal value of CV (OR = 2.07, 95% confidence interval [CI] 1.39–3.10) and HEX (OR = 2.04, 95% CI 1.29–3.23), adjusted for potential confounders, indicating that the high myopia was associated with the abnormal values of CV and HEX. Further adjustment for contact lenses wear partly attenuated these associations. Association between the SER and ECD was not detected.

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Endothelial Cell Density and Central Corneal Thickness following Penetrating Keratoplasty of Acanthamoeba Keratitis Patients – A Retrospective Cross-Sectional Observational Study

Klinische Monatsblätter für Augenheilkunde ◽

10.1055/a-1353-5171 ◽

2021 ◽

Author(s):

Lei Shi ◽

Fabian Norbert Fries ◽

Kassandra Xanthopoulou ◽

Tanja Stachon ◽

Loay Daas ◽

...

Keyword(s):

Endothelial Cell ◽

Observational Study ◽

Cell Density ◽

Central Corneal Thickness ◽

Penetrating Keratoplasty ◽

Corneal Thickness ◽

Acanthamoeba Keratitis ◽

Endothelial Cell Density ◽

Cross Sectional ◽

Time Point

Abstract Purpose To analyze endothelial cell density (ECD) and central corneal thickness (CCT) following penetrating keratoplasty (PKP) in Acanthamoeba keratitis (AK) patients. Patients and Methods In this retrospective, clinical, single-center, cross-sectional, observational study, patients were enrolled who underwent PKP at the Department of Ophthalmology of Saarland University Medical Center, Homburg/Saar, Germany between May 2008 and December 2016 with the diagnosis of AK. In all, 33 eyes of 33 patients (14 males, 42%) were enrolled; their mean age at the time of surgery was 39.5 ± 14.3 years. Postoperatively, AK patients received topical polyhexamethylene biguanide, propamidine isethionate, neomycin sulphate/gramicidin/polymixin B sulfate, and prednisolone acetate eye drops (5 ×/day each), and the topical treatment was tapered sequentially with 1 drop every 6 weeks over 6 months. CCT was recorded using Pentacam HR Scheimpflug tomography and ECD with the EM-3000 specular microscope before surgery and 3 and 6 months after surgery as well as after the first and second (complete) suture removal. Results ECD tended to decrease significantly from the time point before surgery (2232 ± 296 cells/mm2) to the time point 3 months after surgery (1914 ± 164 cells/mm2; p = 0.080) and to the time point after the first suture removal (1886 ± 557 cells/mm2; p = 0.066) and decrease significantly to the time point after the second suture removal (1650 ± 446 cells/mm2; p = 0.028). CCT did not change significantly over the analyzed time period (p ≥ 0.475). Conclusion In AK, endothelial cell loss does not seem to be accelerated following PKP, despite the postoperative use of diamidine and biguanide. A subsequent prospective comparative study should confirm our retrospective longitudinal analysis.

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Plasmin-induced reduction of heparan sulfate in cultured vascular endothelial cell layer

Thrombosis Research ◽

10.1016/0049-3848(94)90001-9 ◽

1994 ◽

Vol 74 (2) ◽

pp. 85-93 ◽

Cited By ~ 4

Author(s):

Toshiyuki Kaji ◽

Syouichi Hiraga ◽

Noriyasu Fujii ◽

Chika Yamamoto ◽

Michiko Sakamoto ◽

...

Keyword(s):

Endothelial Cell ◽

Heparan Sulfate ◽

Cell Layer ◽

Vascular Endothelial Cell ◽

Vascular Endothelial ◽

Endothelial Cell Layer

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Corneal Biomechanical Properties in Varying Severities of Myopia

Frontiers in Bioengineering and Biotechnology ◽

10.3389/fbioe.2020.595330 ◽

2021 ◽

Vol 8 ◽

Author(s):

Mohammad-Reza Sedaghat ◽

Hamed Momeni-Moghaddam ◽

Abbas Azimi ◽

Zohreh Fakhimi ◽

Mohammed Ziaei ◽

...

Keyword(s):

Axial Length ◽

Corneal Thickness ◽

Biomechanical Properties ◽

Cross Sectional Study ◽

Geometrical Parameters ◽

Cross Sectional ◽

Corvis St ◽

Multiple Parameters ◽

Inverse Radius ◽

Biomechanical Parameters

Purpose: To investigate corneal biomechanical response parameters in varying degrees of myopia and their correlation with corneal geometrical parameters and axial length.Methods: In this prospective cross-sectional study, 172 eyes of 172 subjects, the severity degree of myopia was categorized into mild, moderate, severe, and extreme myopia. Cycloplegic refraction, corneal tomography using Pentacam HR, corneal biomechanical assessment using Corvis ST and Ocular Response Analyser (ORA), and ocular biometry using IOLMaster 700 were performed for all subjects. A general linear model was used to compare biomechanical parameters in various degrees of myopia, while central corneal thickness (CCT) and biomechanically corrected intraocular pressure (bIOP) were considered as covariates. Multiple linear regression was used to investigate the relationship between corneal biomechanical parameters with spherical equivalent (SE), axial length (AXL), bIOP, mean keratometry (Mean KR), and CCT.Results: Corneal biomechanical parameters assessed by Corvis ST that showed significant differences among the groups were second applanation length (AL2, p = 0.035), highest concavity radius (HCR, p < 0.001), deformation amplitude (DA, p < 0.001), peak distance (PD, p = 0.022), integrated inverse radius (IR, p < 0.001) and DA ratio (DAR, p = 0.004), while there were no significant differences in the means of pressure-derived parameters of ORA between groups. Multiple regression analysis showed all parameters of Corvis ST have significant relationships with level of myopia (SE, AXL, Mean KR), except AL1 and AL2. Significant biomechanical parameters showed progressive reduction in corneal stiffness with increasing myopia (either with greater negative SE or greater AXL), independent of IOP and CCT. Also, corneal hysteresis (CH) or ability to dissipate energy from the ORA decreased with increasing level of myopia.Conclusions: Dynamic corneal response assessed by Corvis ST shows evidence of biomechanical changes consistent with decreasing stiffness with increasing levels of myopia in multiple parameters. The strongest correlations were with highest concavity parameters where the sclera influence is maximal.

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Prospective predictors of sustainment of multiple EBPs in a system-driven implementation context: Examining sustained delivery based on administrative claims

Implementation Research and Practice ◽

10.1177/26334895211057884 ◽

2021 ◽

Vol 2 ◽

pp. 263348952110578

Author(s):

Anna S. Lau ◽

Teresa Lind ◽

Mojdeh Motamedi ◽

Joyce H. L. Lui ◽

Mary Kuckertz ◽

...

Keyword(s):

Large Scale ◽

Organizational Context ◽

Scale Up ◽

Volume Ratio ◽

Organizational Factors ◽

Self Report ◽

Administrative Claims ◽

Sustained Delivery ◽

Cross Sectional ◽

Program Leaders

Background System-driven scale-up of multiple evidence-based practices (EBPs) is an increasingly common method used in public mental health to improve care. However, there are little data on the long-term sustained delivery of EBPs within these efforts, and previous studies have relied on retrospective self-report within cross-sectional studies. This study identified prospective predictors of sustained EBP delivery at the EBP-, therapist-, and organizational-levels using survey and administrative claims data within a large-scale system-driven implementation effort. Methods 777 therapists and 162 program leaders delivering at least one of six EBPs of interest completed surveys assessing perceptions of EBPs and organizational context. These surveys were linked to administrative data to examine prospective predictors of therapists’ EBP delivery over 33 months. Results Five of the six EBPs implemented showed sustained delivery in the system, with volume varying by EBP. Although total EBP claim volume per therapist decreased over time, the volume ratio (ratio of EBP-specific claims to total EBP and non-EBP claims) stayed relatively stable. Multilevel models revealed that EBPs that required consultation, had unstructured content, higher therapist self-efficacy with the EBP, and more positive program leader perceptions of the EBP were associated with greater sustained volume and volume ratio of the EBP. Therapists who were trained in fewer EBPs, who were unlicensed, and who worked in agencies rated by program leaders as lower on organizational staff autonomy and stress showed greater sustained EBP volume and volume ratio. Finally, more direct service hours per week provided by therapist predicted greater sustained EBP volume, but lower volume ratio. Conclusions The results point to the importance of EBP, therapist, and organizational factors that may be targeted in implementation strategies to promote the sustainment of EBPs.

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Quantitative assessment of lung microstructure in healthy mice using an MR-based 3He lung morphometry technique

Journal of Applied Physiology ◽

10.1152/japplphysiol.00736.2010 ◽

2010 ◽

Vol 109 (6) ◽

pp. 1592-1599 ◽

Cited By ~ 40

Author(s):

E. Osmanagic ◽

A. L. Sukstanskii ◽

J. D. Quirk ◽

J. C. Woods ◽

R. A. Pierce ◽

...

Keyword(s):

Ex Vivo ◽

Volume Ratio ◽

Gas Diffusion ◽

Published Data ◽

Geometrical Parameters ◽

Small Animals ◽

Mean Values ◽

In Vivo Experiments ◽

Lung Morphometry

The recently developed technique of lung morphometry using hyperpolarized 3He diffusion magnetic resonance (MR) (Yablonskiy DA, Sukstanskii AL, Woods JC, Gierada DS, Quirk JD, Hogg JC, Cooper JD, Conradi MS. J Appl Physiol 107: 1258–1265, 2009) permits in vivo study of lung microstructure at the alveolar level. Originally proposed for human lungs, it also has the potential to study small animals. The technique relies on theoretical developments in the area of gas diffusion in lungs linking the diffusion attenuated MR signal to the lung microstructure. To adapt this technique to small animals, certain modifications in MR protocol and data analysis are required, reflecting the smaller size of mouse alveoli and acinar airways. This is the subject of the present paper. Herein, we established empirical relationships relating diffusion measurements to geometrical parameters of lung acinar airways with dimensions typical for mice and rats by using simulations of diffusion in the airways. We have also adjusted the MR protocol to acquire data with much shorter diffusion times compared with humans to accommodate the substantially smaller acinar airway length. We apply this technique to study mouse lungs ex vivo. Our MR-based measurements yield mean values of lung surface-to-volume ratio of 670 cm−1, alveolar density of 3,200 per mm3, alveolar depth of 55 μm, and mean chord length of 62 μm, all consistent with published data obtained histologically in mice by unbiased methods. The proposed technique can be used for in vivo experiments, opening a door for longitudinal studies of lung morphometry in mice and other small animals.

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Arterial stiffness and dementia pathology

Neurology ◽

10.1212/wnl.0000000000005259 ◽

2018 ◽

Vol 90 (14) ◽

pp. e1248-e1256 ◽

Cited By ~ 42

Author(s):

Timothy M. Hughes ◽

Lynne E. Wagenknecht ◽

Suzanne Craft ◽

Akiva Mintz ◽

Gerardo Heiss ◽

...

Keyword(s):

White Matter ◽

Arterial Stiffness ◽

Small Vessel Disease ◽

Brain Mri ◽

Volume Ratio ◽

Cognitive Testing ◽

White Matter Hyperintensity ◽

Cross Sectional ◽

Brain Volumes ◽

Atherosclerosis Risk In Communities

ObjectiveArterial stiffness has been associated with evidence of cerebral small vessel disease (cSVD) and fibrillar β-amyloid (Aβ) deposition in the brain. These complex relationships have not been examined in racially and cognitively diverse cohorts.MethodsThe Atherosclerosis Risk in Communities (ARIC)–Neurocognitive Study collected detailed cognitive testing for adjudication of dementia and mild cognitive impairment (MCI), brain MRI, and arterial stiffness by pulse wave velocity (PWV, carotid-femoral [cfPWV] and heart-carotid [hcPWV]). The ARIC-PET ancillary study added Aβ imaging using florbetapir ([18F]-AV-45) to obtain standardized uptake volume ratios and defined global Aβ-positivity as standardized uptake volume ratio >1.2. One-SD increase in PWV was related to brain volume, MRI-defined cSVD (e.g., cerebral microbleeds and white matter hyperintensity), and cortical Aβ deposition adjusted for age, body mass index, sex, race, and APOE ε4 status. We examined the cross-sectional relationships including interactions by race, APOE ε4 status, and cognition.ResultsAmong the 320 ARIC-PET participants (76 [5] years, 45% black, 27% MCI), greater central stiffness (hcPWV) was associated with greater Aβ deposition (odds ratio [OR] = 1.31, 95% confidence interval [CI] 1.01–1.71). Greater central stiffness (cfPWV) was significantly associated with having lower brain volumes in Alzheimer disease–susceptible regions (in mm3, β = −1.5 [0.7 SD], p = 0.03) and high white matter hyperintensity burden (OR = 1.6, 95% CI 1.2–2.1). Furthermore, cfPWV was associated with a higher odds of concomitant high white matter hyperintensity and Aβ-positive scans (OR = 1.4, 95% CI 1.1–2.1). These associations were strongest among individuals with MCI and did not differ by race or APOE ε4 status.ConclusionsArterial stiffness, measured by PWV, is an emerging risk factor for dementia through its repeated relationships with cognition, cSVD, and Aβ deposition.

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Estimation of Nusselt Number in Microchannels of Arbitrary Cross-Section With Constant Axial Heat Flux

ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels ◽

10.1115/icnmm2008-62198 ◽

2008 ◽

Cited By ~ 1

Author(s):

Ehsan Sadeghi ◽

Majid Bahrami ◽

Ned Djilali

Keyword(s):

Heat Flux ◽

Nusselt Number ◽

Cross Section ◽

Cross Sections ◽

Numerical Solutions ◽

Arbitrary Cross Section ◽

Geometrical Parameters ◽

Thermal Systems ◽

Cross Sectional ◽

Axial Heat

In many practical instances such as basic design, parametric study, and optimization analysis of thermal systems, it is often very convenient to have closed form relations to obtain the trends and a reasonable estimate of the Nusselt number. However, finding exact solutions for many practical singly-connected cross-sections, such as trapezoidal microchannels, is complex. In the present study, the square root of cross-sectional area is proposed as the characteristic length scale for Nusselt number. Using analytical solutions of rectangular, elliptical, and triangular ducts, a compact model for estimation of Nusselt number of fully-developed, laminar flow in microchannels of arbitrary cross-sections with “H1” boundary condition (constant axial wall heat flux with constant peripheral wall temperature) is developed. The proposed model is only a function of geometrical parameters of the cross-section, i.e., area, perimeter, and polar moment of inertia. The present model is verified against analytical and numerical solutions for a wide variety of cross-sections with a maximum difference on the order of 9%.

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