A historical review of experimental imaging of the beating heart coronary microcirculation in vivo

In coronary resistance vessels, endothelium-derived hyperpolarizing factor (EDHF) plays an important role in endothelium-dependent vasodilation. EDHF has been proposed to be formed through cytochrome P-450 monooxygenase metabolism of arachidonic acid (AA). Our hypothesis was that AA-induced coronary microvascular dilation is mediated in part through a cytochrome P-450 pathway. The canine coronary microcirculation was studied in vivo (beating heart preparation) and in vitro (isolated microvessels). Nitric oxide synthase (NOS) ( N ω-nitro-l-arginine, 100 μM) and cyclooxygenase (indomethacin, 10 μM) or cytochrome P-450 (clotrimazole, 2 μM) inhibition did not alter AA-induced dilation. However, when a Ca2+-activated K+ channel channel or cytochrome P-450 antagonist was used in combination with NOS and cyclooxygenase inhibitors, AA-induced dilation was attenuated. We also show a negative feedback by NO on NOS-cyclooxygenase-resistant AA-induced dilation. We conclude that AA-induced dilation is attenuated by cytochrome P-450 inhibitors, but only when combined with inhibitors of cyclooxygenase and NOS. Therefore, redundant pathways appear to mediate the AA response in the canine coronary microcirculation.

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A Brief History of the Discovery of Amelogenin Nanoribbons In Vitro and In Vivo

Journal of Dental Research ◽

10.1177/00220345211043463 ◽

2021 ◽

pp. 002203452110434

Author(s):

Y. Bai ◽

J. Bonde ◽

K.M.M. Carneiro ◽

Y. Zhang ◽

W. Li ◽

...

Keyword(s):

Recombinant Proteins ◽

Protein Structures ◽

Historical Review ◽

Limited Information ◽

Transmission Electron Microscopy Analysis ◽

Electron Microscopy Analysis ◽

History Of ◽

The 1960S

Without evidence for an organic framework, biological and biochemical processes observed during amelogenesis provided limited information on how extracellular matrix proteins control the development of the complex fibrous architecture of human enamel. Over a decade ago, amelogenin nanoribbons were first observed from recombinant proteins during in vitro mineralization experiments in our laboratory. In enamel from mice lacking the enzyme kallikrein 4 (KLK4), we later uncovered ribbon-like protein structures that matched the morphology, width, and thickness of the nanoribbons assembled by recombinant proteins. Interestingly, similar structures had already been described since the 1960s, when enamel sections from various mammals were demineralized and stained for transmission electron microscopy analysis. However, at that time, researchers were not aware of the ability of amelogenin to form nanoribbons and instead associated the filamentous nanostructures with possible imprints of mineral ribbons in the gel-like matrix of developing enamel. Further evidence for the significance of amelogenin nanoribbons for enamel development was stipulated when recent mineralization experiments succeeded in templating and orienting the growth of apatite ribbons along the protein nanoribbon framework. This article provides a brief historical review of the discovery of amelogenin nanoribbons in our laboratory in the context of reports by others on similar structures in the developing enamel matrix.

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Myocardial Microcirculation in the Beating Heart — In Vivo Microscopic Studies

Coronary Circulation - Developments in Cardiovascular Medicine ◽

10.1007/978-94-009-3369-9_8 ◽

1987 ◽

pp. 88-94 ◽

Cited By ~ 7

Author(s):

H. Tillmanns ◽

H. Leinberger ◽

F. J. Neumann ◽

M. Steinhausen ◽

N. Parekh ◽

...

Keyword(s):

Beating Heart ◽

Myocardial Microcirculation ◽

Microscopic Studies

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Nitric oxide limits coronary vasoconstriction by a shear stress-dependent mechanism

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.2001.281.2.h796 ◽

2001 ◽

Vol 281 (2) ◽

pp. H796-H803 ◽

Cited By ~ 30

Author(s):

David W. Stepp ◽

Daphne Merkus ◽

Yasuhiro Nishikawa ◽

William M. Chilian

Keyword(s):

Nitric Oxide ◽

Shear Stress ◽

Coronary Microcirculation ◽

Shear Stresses ◽

No Production ◽

Small Arteries ◽

Inner Diameter ◽

Stress Dependent ◽

Dependent Mechanism

Increases in shear stress promote coronary vasodilation by stimulating the production of nitric oxide (NO). Whether shear stress-induced NO production also limits vasoconstriction in the coronary microcirculation in vivo is unknown. Accordingly, we measured microvascular diameter and flow velocity in the beating heart along with estimated blood viscosity to calculate shear stress during vasoconstriction with endothelin or vasopressin. Measurements were repeated in the presence of N G-monomethyl-l-arginine (l-NMMA) to inhibit NO production and BQ-788 to block NO-linked endothelin type B receptors. BQ-788 did not augment steady-state constriction to endothelin, suggesting that NO production via activation of this receptor is inconsequential. l-NMMA potentiated constriction to both agonists, particularly in small arteries (inner diameter >120 μm). Shear stresses in small arteries were elevated during constriction and further elevated during constriction after l-NMMA. These observations suggest that NO production limits vasoconstriction in the coronary microcirculation and that the principal stimulus for this governance is elevated shear stress. The degree of shear stress moderation of constriction is heterogeneously distributed, with small arteries displaying a higher degree of shear stress regulation than arterioles. These results provide the strongest evidence to date that shear stress-mediated production of NO exerts a “braking” influence on constriction in the coronary microcirculation.

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Aortic perfusion pressure as early determinant of beta-isomyosin expression in perfused hearts

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1992.263.5.h1537 ◽

1992 ◽

Vol 263 (5) ◽

pp. H1537-H1545

Author(s):

C. Delcayre ◽

D. Klug ◽

V. T. Nguyen ◽

C. Mouas ◽

B. Swynghedauw

Keyword(s):

Protein Synthesis ◽

Total Protein ◽

Stress Protein ◽

Pressure Overload ◽

Aortic Pressure ◽

Mechanical Stimulus ◽

Beating Heart ◽

Specific Gene ◽

Coronary Pressure

Pressure overload in vivo induces an increase in cardiac protooncogene and stress protein expression that may initiate the long-term genetic changes observed in hypertrophy. To known whether mechanical stimulus is linked to specific gene transcription, expression of immediate early genes and synthesis of total proteins and myosin heavy chains (MHCs) were studied in beating and KCl-arrested isolated rat hearts perfused for 2 h under various coronary pressures. The main result of this study is that in the beating heart an augmentation of aortic pressure from 60 to 120 mmHg results in a pronounced enhancement of the synthesis of MHC (+59%) and of the expression of the beta-MHC isomyosin mRNA (iso-mRNA; +104%). Also, total protein synthesis and the amounts of poly-(A)+, c-fos, c-myc, and heat-shock protein HSP68 mRNAs were increased. To arrest the heart at 60 mmHg has no effect on total protein synthesis and on the amounts of poly(A)+, alpha-MHC and beta-MHC iso-mRNAs, and mRNAs coding for oncoproteins, but the synthesis of MHC decreased by 24%. By contrast with what we have observed in the beating heart, the augmentation of the coronary pressure in the arrested heart stimulates total protein synthesis and increases the amount of poly(A)+, c-fos, c-myc, and HSP68 mRNAs but has no effect on the expression of both MHC iso-mRNAs. In conclusion, the activation of myosin synthesis by high coronary pressure in this model has mainly a pretranslational origin when the heart is beating.(ABSTRACT TRUNCATED AT 250 WORDS)

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In vivo location and mechanism of EDHF-mediated vasodilation in canine coronary microcirculation

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1999.277.3.h1252 ◽

1999 ◽

Vol 277 (3) ◽

pp. H1252-H1259 ◽

Cited By ~ 29

Author(s):

Yasuhiro Nishikawa ◽

David W. Stepp ◽

William M. Chilian

Keyword(s):

Nitric Oxide ◽

Potassium Channels ◽

Potassium Channel ◽

Direct Evidence ◽

Coronary Microcirculation ◽

Combined Administration ◽

Cytochrome P 450 ◽

Coronary Arterioles

Responses of epicardial coronary arterioles to ACh were measured using stroboscopic fluorescence microangiography in dogs ( n = 38). ACh (0.1 and 0.5 μg ⋅ kg−1 ⋅ min−1ic) dilated small (<100 μm, 11 ± 2 and 19 ± 2%, respectively) and large (>100 μm, 6 ± 3 and 13 ± 3%, respectively) arterioles at baseline. Combined administration of N ω-monomethyl-l-arginine (l-NMMA; 1.0 μmol/min ic) and indomethacin (10 mg/kg iv) eliminated ACh-induced dilation in large coronary arterioles but only partially attenuated that in small arterioles. Suffusion of a buffer containing 60 mM KCl (high KCl) completely abolished cromakalim-induced dilation in arterioles and in combination with l-NMMA plus indomethacin completely blocked ACh-induced dilation in small arterioles. This indicated that the vasodilation to ACh that persists in small arterioles after administration of l-NMMA and indomethacin is mediated via a hyperpolarizing factor. The ACh-induced vasodilation remaining after l-NMMA and indomethacin was completely blocked by the large-conductance potassium-channel antagonist iberiotoxin or by epicardial suffusion of miconazole or metyrapone, inhibitors of cytochrome P-450 enzymes. These observations are consistent with the view that endothelium-derived hyperpolarizing factor (EDHF) is a product of cytochrome P-450 enzymes and produces vasodilation by the opening of large-conductance potassium channels. We conclude that ACh-induced dilation in large coronary arterioles is mediated mainly by nitric oxide (NO), whereas, in small arterioles both NO and EDHF mediate dilation to ACh. These data provide the first direct evidence for an in vivo role of EDHF in small coronary arterioles.

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