Decreased inspired oxygen stimulates de novo formation of coronary collaterals in adult heart

Pial collaterals provide protection in stroke. Evidence suggests their formation late during gestation (collaterogenesis) is driven by reduced oxygen levels in the cerebral watersheds. The purpose of this study was to determine if collaterogenesis can be re-activated in the adult to induce formation of additional collaterals (“neo-collateral formation”, NCF). Mice were gradually acclimated to reduced inspired oxygen (FIO2) and maintained at 12, 10, 8.5 or 7% for two-to-eight weeks. Hypoxemia induced “dose”-dependent NCF and remodeling of native collaterals, and decreased infarct volume after permanent MCA occlusion. In contrast, no formation occurred of addition collateral-like intra-tree anastomoses, PComs, or branches within the MCA tree. Hypoxic NCF, remodeling and infarct protection were durable, i.e. retained for at least six weeks after return to normoxia. Hypoxia increased expression of Hif2α, Vegfa, Rabep2, Angpt2, Tie2 and Cxcr4. Neo-collateral formation was abolished in mice lacking Rabep2, a novel gene involved in VEGFA→Flk1 signaling and required for formation of collaterals during development, and inhibited by knockdown of Vegfa, Flk1 and Cxcr4. Rabep2-dependent NCF was also induced by permanent MCA occlusion. This is the first report that hypoxia induces new pial collaterals to form. Hypoxia- and occlusion-induced neo-collateral formation provide models to study collaterogenesis in the adult.

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De novo tacrolimus extended‐release tablets (LCPT) versus twice‐daily tacrolimus in adult heart transplantation: Results of a single‐center non‐inferiority matched control trial

Clinical Transplantation ◽

10.1111/ctr.14487 ◽

2021 ◽

Author(s):

Johanna S. van Zyl ◽

Teena Sam ◽

Donna M. Clark ◽

Joost Felius ◽

Amanda K. Doss ◽

...

Keyword(s):

Heart Transplantation ◽

Extended Release ◽

Matched Control ◽

De Novo ◽

Single Center ◽

Adult Heart

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Identification of a multipotent Twist2-expressing cell population in the adult heart

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1800526115 ◽

2018 ◽

Vol 115 (36) ◽

pp. E8430-E8439 ◽

Cited By ~ 4

Author(s):

Yi-Li Min ◽

Priscilla Jaichander ◽

Efrain Sanchez-Ortiz ◽

Svetlana Bezprozvannaya ◽

Venkat S. Malladi ◽

...

Keyword(s):

Cell Population ◽

De Novo ◽

Lineage Tracing ◽

Cell Fates ◽

Mesodermal Cell ◽

Adult Heart ◽

Reporter Mice ◽

Unique Cell ◽

Cellular Components

Twist transcription factors function as ancestral regulators of mesodermal cell fates in organisms ranging from Drosophila to mammals. Through lineage tracing of Twist2 (Tw2)-expressing cells with tamoxifen-inducible Tw2-CreERT2 and tdTomato (tdTO) reporter mice, we discovered a unique cell population that progressively contributes to cardiomyocytes (CMs), endothelial cells, and fibroblasts in the adult heart. Clonal analysis confirmed the ability of Tw2-derived tdTO+ (Tw2-tdTO+) cells to form CMs in vitro. Within the adult heart, Tw2-tdTO+ CMs accounted for ∼13% of total CMs, the majority of which resulted from fusion of Tw2-tdTO+ cells with existing CMs. Tw2-tdTO+ cells also contribute to cardiac remodeling after injury. We conclude that Tw2-tdTO+ cells participate in lifelong maintenance of cardiac function, at least in part through de novo formation of CMs and fusion with preexisting CMs, as well as in the genesis of other cellular components of the adult heart.

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The Morphology of the Rat Kidney Following Folic Acid Administration

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100067996 ◽

1970 ◽

Vol 28 ◽

pp. 200-201

Author(s):

Aline Byrnes ◽

Elsa E. Ramos ◽

Minoru Suzuki ◽

E.D. Mayfield

Keyword(s):

Folic Acid ◽

De Novo ◽

Specific Activity ◽

Rat Kidney ◽

Present Report ◽

Intracellular Localization ◽

Male Rats ◽

Renal Hypertrophy ◽

Electron Microscopic ◽

Biochemical Alterations

Renal hypertrophy was induced in 100 g male rats by the injection of 250 mg folic acid (FA) dissolved in 0.3 M NaHCO3/kg body weight (i.v.). Preliminary studies of the biochemical alterations in ribonucleic acid (RNA) metabolism of the renal tissue have been reported recently (1). They are: RNA content and concentration, orotic acid-c14 incorporation into RNA and acid soluble nucleotide pool, intracellular localization of the newly synthesized RNA, and the specific activity of enzymes of the de novo pyrimidine biosynthesis pathway. The present report describes the light and electron microscopic observations in these animals. For light microscopy, kidney slices were fixed in formalin, embedded, sectioned, and stained with H & E and PAS.

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Molecular and Microscopic Analysis of Altered Gene Expression in Transgenic and Gene Targeted Mice

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100162521 ◽

1996 ◽

Vol 54 ◽

pp. 12-13

Author(s):

W. K. Jones ◽

J. Robbins

Keyword(s):

Gene Expression ◽

Pulmonary Veins ◽

Microscopic Analysis ◽

Mouse Tissue ◽

Adult Heart ◽

Heavy Chains ◽

Altered Gene Expression ◽

Altered Gene ◽

Pulmonary Myocardium

Two myosin heavy chains (MyHC) are expressed in the mammalian heart and are differentially regulated during development. In the mouse, the α-MyHC is expressed constitutively in the atrium. At birth, the β-MyHC is downregulated and replaced by the α-MyHC, which is the sole cardiac MyHC isoform in the adult heart. We have employed transgenic and gene-targeting methodologies to study the regulation of cardiac MyHC gene expression and the functional and developmental consequences of altered α-MyHC expression in the mouse.We previously characterized an α-MyHC promoter capable of driving tissue-specific and developmentally correct expression of a CAT (chloramphenicol acetyltransferase) marker in the mouse. Tissue surveys detected a small amount of CAT activity in the lung (Fig. 1a). The results of in situ hybridization analyses indicated that the pattern of CAT transcript in the adult heart (Fig. 1b, top panel) is the same as that of α-MyHC (Fig. 1b, lower panel). The α-MyHC gene is expressed in a layer of cardiac muscle (pulmonary myocardium) associated with the pulmonary veins (Fig. 1c). These studies extend our understanding of α-MyHC expression and delimit a third cardiac compartment.

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Early ossicle growth in the regenerating disc of a brittle star

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100169559 ◽

1994 ◽

Vol 52 ◽

pp. 364-365

Author(s):

M. Shlepr ◽

R. L. Turner

Keyword(s):

Cell Membrane ◽

Light Microscopy ◽

De Novo ◽

Current Model ◽

Syncytium Formation ◽

Brittle Star ◽

Intracellular Location ◽

Limited Volume ◽

Tissue Calcification

Calcification in the echinoderms occurs within a limited-volume cavity enclosed by cytoplasmic extensions of the mineral depositing cells, the sclerocytes. The current model of this process maintains that the sheath formed from these cytoplasmic extensions is syncytial. Prior studies indicate that syncytium formation might be dependent on sclerocyte density and not required for calcification. This model further envisions that ossicles formed de novo nucleate and grow intracellularly until the ossicle effectively outgrows the vacuole. Continued ossicle growth occurs within the sheath but external to the cell membrane. The initial intracellular location has been confirmed only for elements of the echinoid tooth.The regenerating aboral disc integument of ophiophragmus filograneus was used to test the current echinoderm calcification model. This tissue is free of calcite fragments, thus avoiding questions of cellular engulfment, and ossicles are formed de novo. The tissue calcification pattern was followed by light microscopy in both living and fixed preparations.

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Arabidopsis 4-COUMAROYL-COA LIGASE 8 contributes to the biosynthesis of the benzenoid ring of coenzyme Q in peroxisomes

Biochemical Journal ◽

10.1042/bcj20190688 ◽

2019 ◽

Vol 476 (22) ◽

pp. 3521-3532

Author(s):

Eric Soubeyrand ◽

Megan Kelly ◽

Shea A. Keene ◽

Ann C. Bernert ◽

Scott Latimer ◽

...

Keyword(s):

Oxidative Metabolism ◽

Time Course ◽

Reverse Genetics ◽

De Novo ◽

Coenzyme Q ◽

Control Level ◽

Wild Type ◽

Fluorescent Reporters ◽

Coa Ligase ◽

Peroxisomal Targeting

Plants have evolved the ability to derive the benzenoid moiety of the respiratory cofactor and antioxidant, ubiquinone (coenzyme Q), either from the β-oxidative metabolism of p-coumarate or from the peroxidative cleavage of kaempferol. Here, isotopic feeding assays, gene co-expression analysis and reverse genetics identified Arabidopsis 4-COUMARATE-COA LIGASE 8 (4-CL8; At5g38120) as a contributor to the β-oxidation of p-coumarate for ubiquinone biosynthesis. The enzyme is part of the same clade (V) of acyl-activating enzymes than At4g19010, a p-coumarate CoA ligase known to play a central role in the conversion of p-coumarate into 4-hydroxybenzoate. A 4-cl8 T-DNA knockout displayed a 20% decrease in ubiquinone content compared with wild-type plants, while 4-CL8 overexpression boosted ubiquinone content up to 150% of the control level. Similarly, the isotopic enrichment of ubiquinone's ring was decreased by 28% in the 4-cl8 knockout as compared with wild-type controls when Phe-[Ring-13C6] was fed to the plants. This metabolic blockage could be bypassed via the exogenous supply of 4-hydroxybenzoate, the product of p-coumarate β-oxidation. Arabidopsis 4-CL8 displays a canonical peroxisomal targeting sequence type 1, and confocal microscopy experiments using fused fluorescent reporters demonstrated that this enzyme is imported into peroxisomes. Time course feeding assays using Phe-[Ring-13C6] in a series of Arabidopsis single and double knockouts blocked in the β-oxidative metabolism of p-coumarate (4-cl8; at4g19010; at4g19010 × 4-cl8), flavonol biosynthesis (flavanone-3-hydroxylase), or both (at4g19010 × flavanone-3-hydroxylase) indicated that continuous high light treatments (500 µE m−2 s−1; 24 h) markedly stimulated the de novo biosynthesis of ubiquinone independently of kaempferol catabolism.

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