Biomedical subjects

E Page

Publications and source records attributed to E Page.

At least 55 records · Page 3Linked to original sources

PubMed1990

Basal and stretch-augmented natriuretic peptide secretion by quiescent rat atria.

Absolute rates of immunoreactive atrial natriuretic peptide (ANP) secretion were measured in vitro at 37 degrees C in noncontracting preparations of combined right and left rat atria at constant distending pressures of 0 or 5.1 mmHg in presence of 0.2 mM extracellular Ca2+ concentration [( Ca2+]o), 10 microM ryanodine, and either 1 microM saxitoxin or 10 microM tetrodotoxin. By systematic deletion of external Na+, K+, Mg2+, Cl-, or HCO3-, and reduction of [Ca2+]o, and by selective ion transport inhibitors, neither net transplasmalemmal fluxes of Na+, Cl-, HCO3-, and Mg2+ nor ryanodine-sensitive Ca2+ release from sarcoplasmic reticulum (SR) was found necessary for stretch augmentation of secretory rate (Ra). Ra 1) was near zero within 20 min when extracellular Na+ concentration = 0 and [Ca2+]o = 20 microM and within 5 min or less after preincubation with caffeine, 8-chlorophenylthioadenosine 3',5'-cyclic monophosphate, or at 18 degrees C; 2) was significantly decreased by Cd2+, Ni2+, the isoquinoline H-7, and trifluoperazine but not 100 microM ryanodine; 3) was increased by neomycin; and 4) had an apparent activation energy of 18.5 +/- 4.1 x 10(3) cal/mol between 23 and 42 degrees C. These experiments strongly implicated transplasmalemmal Ca2+ influx and cAMP but not SR Ca2+ release in control of Ra under the experimental conditions studied.

Amiloride↗

PubMed1990

[A rare complication of thoracic radiotherapy: auriculoventricular block. Apropos of a case and review of the literature].

The authors report the case of a 30-year old patient who presented atrioventricular block 12 years after mediastinal radiation treatment of Hodgkin's disease. This patient had been monitored in the service for 3 years after the insertion of a pacemaker. A review of the literature, identified 15 cases of post-radiation AV block. The AV block was subnodal in the 7 cases which were subjected to endocavitary recording.

Adult↗

PubMed1989

Localization of wheat-germ agglutinin-binding sites in the Golgi complex of cultured rat atrial myocytes.

In the Golgi region of cultured rat atrial myocytes, condensed secretory protein was seen in Golgi-associated tubules or cisternae which lay beyond, and often separated from, the remainder of the Golgi stacks. These structures appeared to be involved in packaging of condensed secretory protein into atrial granules. Binding sites of HRP-conjugated wheat-germ agglutinin (WGA) in saponin-treated cultured atrial myocytes were examined by electron microscopy with special reference to atrial granules and the tubular structures associated with the Golgi stacks. HRP reaction products were observed in both trans-cisternae of the Golgi stacks and the associated tubular structures. While the majority of atrial granules were devoid of reaction products, some granules, which were connected to the WGA-positive tubular structures in the vicinity of the Golgi trans-cisternae, showed HRP reaction products at their connected necks. Similar results were obtained when sections of the cells embedded in Lowicryl K4M were labeled with WGA coupled to colloidal gold (G-WGA); the Golgi complex was G-WGA positive, whereas no specific binding of G-WGA to atrial granules was observed. These results suggest that glycoproteins and/or glycolipids with oligosaccharides recognized by WGA in the Golgi transcisternae, may be separated from atrial natriuretic peptides which are packaged into atrial granules.

Animals↗

PubMed1989

Acral localized acquired cutis laxa.

We report the first case of acral localized acquired cutis laxa. The skin laxity was preceded by swelling of the fingers and toes and by the appearance of papular urticaria. Dapsone therapy was effective in controlling the swelling. Examination of skin biopsy specimens showed fragmentation and almost total loss of elastic fibers in the areas of cutis laxa. Electron microscopy showed no abnormalities in elastic structure and function in unaffected skin. In addition, electron microscopic examination of an urticarial lesion showed a neutrophilic dermatosis with polymorphonuclear leukocytes attached to the surface of either normal elastic fibers or fibers showing early degenerative changes. These findings suggest that there is no primary defect in the elastic fibers and that the polymorphonuclear leukocytes play a significant role in the destruction of the elastic fibers and the subsequent development of cutis laxa in this case.

Adult↗

PubMed1989

Determinants of atrial natriuretic peptide secretion in cultured atrial myocytes.

Atrial natriuretic peptide (ANP) secretion by atrial myocytes in 7- to 8-day primary cultures from adult rats was measured by radioimmunoassay under conditions designed to separate primary effects on secretion from effects caused by contractions. Abolishing contraction with 10 microM tetrodotoxin significantly reduced ANP accumulated in 2 h. Raising external Ca2+ concentration from 0.2 to 1.2 mM in the presence of tetrodotoxin did not increase ANP secretion. Substantial ANP secretion persisted in a nominally Ca2+-free medium containing 10 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) and was not diminished by 100 microM ryanodine. In the presence of EGTA, 100 nM 12-O-tetradecanoylphorbol 13-acetate (TPA) significantly increased ANP secretion; this increment was unaffected by 100 microM ryanodine. These experiments suggest 1) that in absence of contractions, ANP secretion requires neither transplasmalemmal Ca2+ influx nor ryanodine-inhibitable Ca2+ release by sarcoplasmic reticulum (SR) and 2) that TPA stimulates ANP secretion without requiring Ca influx or ryanodine-inhibitable SR Ca release.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1989

Cardiac gap junctions and gap junction-associated vesicles: ultrastructural comparison of in situ negative staining with conventional positive staining.

By comparing in situ negative staining of mammalian heart muscle using La(NO3)3 with conventional positive staining by uranium and lead salts, we showed that 1) the membrane area of rat cardiac gap junctions (GJs) at the intercalated disks is threefold to fourfold greater than previously thought; 2) connexon arrays of cardiac GJ are subdivided into microdomains by connexon-free aisles; 3) profiles of GJ-associated vesicles (GJAVs) of plasmalemmal origin (which are present extracellularly and sharply localized at three extracellular sites) are paired to form GJs with each other and with myocyte plasmalemma; 4) some GJAVs contain arrays of assembled connexons; and 5) myocytes contain intracytoplasmic complexes lying within cylindrical or cigar-shaped membranes and consisting of GJs and multiple vesicles apparently dissociating from these GJs.

Animals↗

PubMed1989

[Detection of parietal lesions using magnetic resonance imaging in arrhythmogenic dysplasia of the right ventricle].

Seven patients with arrhythmogenic right ventricular dysplasia were explored by magnetic resonance imaging (MRI), using the spin-echo technique (TR = the patient's own RR cycle; TE = 28 ms, 56 ms, 84 ms) with multiple, contiguous, 7 to 10 mm thick sections performed in two planes: axial plus sagittal or frontal planes. In 5 out of 7 patients, MRI showed dysplastic lesions in the right ventricular wall presenting typically as fat-like high signals contrasting with the normal myocardium. In 2 patients, no lesion was clearly visualized. The parietal lesions were located in the anterior wall of the right ventricle and conus arteriosus in 5 cases and in the lower wall of the right ventricle in one patient who had two dysplastic areas. In 3 patients the lesions extended up to the tip of the interventricular septum and of the left ventricle. In the 2 patients whose lesions were most extensive, their predominance in the subepicardial region and the concordance between the sites of abnormalities at MRI and angiography were clearly observed. Thus, despite its present technical limitations MRI seems to be one of the first techniques capable of visualizing the parietal lesions in patients with arrhythmogenic right ventricular dysplasia.

Adult↗

PubMed1988

Inhibition of atrial natriuretic peptide secretion by forskolin in noncontracting cultured atrial myocytes.

Secretory rates for immunoreactive atrial natriuretic peptide (ANP) by 7 - 8 day-old primary cultures of atrial myocytes from adult rats (with myocyte contraction inhibited by tetrodotoxin (TTX)) were (a) constant for at least two hours, and (b) significantly slowed by forskolin (1, 5, and 25 microM), dibutyryl cyclic adenosine monophosphate (1 mM), or isobutylmethylxanthine (100 microM). The substantial rates of ANP secretion which persisted in cells rendered noncontracting either by inhibiting Ca2+ influx via reduction of external [Ca2+] to less than 10(-7) M or by inhibiting sarcoplasmic reticulum Ca2+ release with 100 microM ryanodine were significantly slowed by 25 microM forskolin, but forskolin sensitivity was lost by cells exposed simultaneously to external Ca2+ concentration of less than 10(-7) M and 100 microM ryanodine. Quiescent myocytes whose ANP secretory rate was depressed by forskolin remained responsive to secretory stimulation by phorbol ester.

1-Methyl-3-isobutylxanthine↗

PubMed1988

Occupational contact dermatitis due to glutaraldehyde in health care workers.

Allergic contact dermatitis to glutaraldehyde was found in 13 health-care workers with hand dermatitis. Concomitant sensitivity to other chemicals was noted in 10. The positive patch test response was only evident for every 2nd observation in 4. The eruption persisted for more than 6 months in 10 subjects. In 5, the skin disease forced the worker to leave his occupation.

Adult↗

PubMed1988

Monensin turns on microtubule-associated translocation of secretory granules in cultured rat atrial myocytes.

We have studied the effect of monensin on microtubule-associated translocation of atrial secretory granules in 5-7-day-old cultures of atrial myocytes from adult rats. Atrial granules and microtubules were localized by immunofluorescent microscopy of myocytes double-labeled with primary antibodies against atrial natriuretic polypeptide (ANP) and alpha-tubulin. In control myocytes, fluorescence due to atrial granules was predominantly localized to the perinuclear region containing the Golgi complex. After exposure for 30 minutes to monensin (0.5-5.0 microM), myocytes transiently contained conspicuous linear arrays of atrial granules associated with cytoplasmic microtubules. Thereafter, ANP fluorescence accumulated in subsarcolemmal foci at the cell periphery, while perinuclear ANP fluorescence faded. The monensin-induced redistribution of atrial granules was observable in both serum-containing and serum-free media and was unaffected by reducing external Ca2+ to low values, by inhibition of sarcoplasmic reticulum Ca2+ release with ryanodine, or by both. The redistribution was prevented by pretreatment with nocodazole, which fragmented microtubules and scattered Golgi complexes and the associated atrial granules throughout the cytoplasm. Radioimmunoassay showed that monensin seemingly decreased the rate of ANP secretion into the medium from 0.15 to 0.11 fmol/(hr.myocyte). These results suggest that monensin turns on microtubule-associated translocation of atrial granules from the perinuclear areas to the cell periphery by modifying the interaction between microtubules and atrial granules. Monensin also promotes movement of atrial granules along the microtubules but does not accelerate the release of ANP.

Animals↗

PubMed1987

The cardiac gap junction protein (Mr 47,000) has a tissue-specific cytoplasmic domain of Mr 17,000 at its carboxy-terminus.

The molecular weight of the heart gap junctional protein subunit was, until recently, believed to be about Mr 28,000-30,000, similar to that of other previously characterized gap junctional proteins. A larger polypeptide of about Mr 44,000-47,000, which undergoes proteolysis during isolation, has recently been proposed as the form of the heart junction protein in vivo. We show here that this entity has the same amino-terminal sequence as the previously characterized Mr 29,000-30,000 component. Thus, the cardiac junctional protein has, at its carboxy-terminus, cytoplasmic domain of Mr 17,000; this domain is absent in the liver protein. These observations provide further evidence that gap junction proteins form a highly diversified family.

Amino Acid Sequence↗

PubMed1987

Human cardiac gap junctions: isolation, ultrastructure, and protein composition.

Recent experiments from our laboratory have shown that the ultrastructure and protein composition of gap junctions isolated from rat ventricles are tissue specific, i.e., markedly different from gap junctions of liver and lens. The differences include a cytoplasmic surface component characteristic for cardiac gap junctions; this component can be visualized by two ultrastructural techniques: as a fuzzy layer in electron micrographs of thin-sectioned junctional pellets and as cytoplasmic surface particles in deep-etched freeze-fractured junctions. The component corresponds to a Mr 17,500 cytoplasmic surface domain of each of the six (Mr 47,000) rat heart gap junctional channel protein subunits that make up the gap junctional channel hexamer known as a connexon. The cytoplasmic surface component is localized at the carboxy-terminal of the subunit. Within the cytoplasmic surface component, rat cardiac gap junctions are cross-linked by disulfide linkages between subunits of the same connexon and between subunits of adjacent connexons. By contrast, the Mr 28,000 liver gap junctional subunit lacks a comparably large cytoplasmic surface component, cytoplasmic surface fuzz, cytoplasmic surface particles, and intra- and interconnexon disulfide linkages. Most of these unique characteristics of cardiac gap junctions were discovered in junctions isolated from rat ventricles. Unlike liver and lens gap junctions, cardiac gap junctions from humans, non-human primates, or other large mammals have not previously been isolated and characterized. Here we report the isolation of unproteolyzed gap junctions from the ventricle of a 24 year-old man with advanced cardiomyopathy whose heart was removed for replacement by a transplanted heart.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Fractionation↗

PubMed1987

Tunneling cell processes in myocytes of stretched mouse atria.

Serial section electron micrographs of mouse atria stretched in vitro show that myocytes have cell processes which tunnel into adjacent myocytes for 8 microns or more. The tunneling cell processes (TCP) (diam 4-6.2 microns) lack myofibrils and organelles associated with atrial peptide secretion. The glycogen-rich TCP cytoplasmic matrix contains conspicuous tubules and vesicles originating from endoplasmic reticulum and resembling free sarcoplasmic reticulum (SR). TCP are surrounded by a plasmalemma derived from their myocyte of origin, the plasmalemma of the tunneled myocyte, and an intervening narrow compartment continuous with the interstitial space. Profiles having the characteristics cytoplasmic structure of TCP are also found both in the interstitial space between myocytes and near the longitudinal terminations where myocyte ends about on the interstitial space. We suggest that TCP tubules and vesicles may proliferate and/or transport in response to stretch, might be free SR, and may respond to stretch-activated changes in ionic composition or potential of the surrounding myocyte and narrow intercellular compartment.

Animals↗

PubMed1986

Separation of cardiac plasmalemma into cell surface and T-tubular components. Distribution of saxitoxin- and nitrendipine-binding sites.

To compare surface sarcolemmal with T-tubular distributions of [3H]saxitoxin (STX)- and [3H]nitrendipine (NTD)-binding sites, we centrifuged membrane vesicles from sheep and bovine ventricles on a 10-40% linear sucrose gradient from which fractions were assayed for STX and NTD binding; for markers of surface sarcolemma (ouabain-sensitive Na,K-ATPase activity, [3H]quinuclidinyl benzilate binding); and for markers of junctional sarcoplasmic reticulum known to be preferentially associated with T-tubules (ryanodine-sensitive Ca2+ uptake, calsequestrin, an Mr 300,000 putative phosphorylatable "foot" protein, and electron microscopically visible junctional sarcoplasmic reticulum-plasmalemma complexes). We identified three distinct peaks in the sucrose gradient, each characterized by significant high and low affinity STX- and high affinity NTD-binding: Peak I (approximately 19% sucrose), highly enriched in surface sarcolemma; Peak III (approximately 36% sucrose), enriched in junctional sarcoplasmic reticulum markers and hence in junctional sarcoplasmic reticulum complexes with T-tubule; and Peak II (approximately 27% sucrose), showing greatest specific STX binding and only moderate NTD binding, enriched in T-tubular membrane, unassociated with junctional sarcoplasmic reticulum. For ventricular myocytes, the ratio NTD sites/STX sites was 2.5 for surface sarcolemma, but only approximately 1.0 for T-tubules. Unlike data published for mammalian skeletal muscle, sheep and beef cardiac NTD receptors were not significantly more concentrated in T-tubular than in surface plasmalemma.

Amphibian Proteins↗

PubMed1986

Rat heart gap junctions as disulfide-bonded connexon multimers: their depolymerization and solubilization in deoxycholate.

Unproteolyzed gap junctions isolated from rat heart and liver were analyzed for the presence of inter-subunit disulfide bonds by sodium dodecylsulfate polyacrylamide gel electrophoresis. Rat cardiac junctions contained multiple disulfide bonds connecting the Mr 47,000 subunits of the same connexon and of different connexons. Inter-subunit disulfide bonds were absent in liver junctions. Unproteolyzed rat heart gap junctions were resistant to deoxycholate in their oxidized state, but dissolved readily in the detergent when the disulfide bonds were cleaved with beta-mercaptoethanol. Disulfide bonding in proteolyzed cardiac junctions was limited to pairs of Mr 29,500 subunits. These junctions were not soluble in deoxycholate even in the presence of beta-mercaptoethanol. These results show that heart and liver junctions differ in their quarternary organization.

Animals↗

PubMed1986

Developmental changes in P-face and E-face particle densities of Xenopus cardiac muscle plasma membrane.

P- and E-face particle densities (PPD and EPD) were measured in electron micrographs of freeze-fractured cardiac sarcolemma from eight developmental stages of Xenopus laevis (stages 33/34 (33 post-otic somite embryos) to 66 (fully metamorphosed juvenile toad], using stereo-imaged replicas. We found striking progressive increases in PPD and EPD, most rapid between stages 33/34 and 37/38; that PPD was significantly greater than EPD at all stages; that both PPD and EPD of stereo-imaged replicas were about X2 greater than corresponding values not stereo-imaged; and that sarcolemmal PPD of late anuran embryonic and post-metamorphosis hearts were significantly greater than our previously determined PPD values for chick late embryo and adult mammalian sarcolemma. We suggest that PPD and EPD depend on how membrane particles segregate during freeze-fracture and on the relative contributions of membrane-spanning and non-membrane-spanning integral membrane protein complexes to each fracture face.

Aging↗

PubMed1986

Ultrastructural features of atrial peptide secretion.

The ultrastructural bases of exocytotic extrusion of atrial peptides were reexamined in electron micrographs of thin-sectioned or freeze-fractured mouse atria. Exocytotic extrusion was demonstrated in both thin-sectioned and freeze-fractured atrial myocytes. Ultrastructural evidence suggested that the necks of plasmalemmal caveolae may constitute preformed pathways for extrusion of secretion from granules fusing with caveolae. Multiple subsarcolemmal foci with peripheral Golgi cisterns and accumulations of granules, indicating peripheral processing of secretory proteins, were striking features of mouse and rat atria, and were present but rare in sheep and dog atria. Conspicuous focal ellipsoidal deposits, a new structure, approximately 1.6-4.6 micron long and approximately 0.8-1.8 micron wide, consisting of amorphous cytoplasmic material that is penetrated peripherally by tubules connecting with secretion-containing "multivesicular bodies," were present in some mouse atrial myocytes, but were absent in myocytes of mouse ventricle and rat, dog, and sheep atria.

Animals↗

PubMed1985

Proteolysis of cardiac gap junctions during their isolation from rat hearts.

Gap junctions (GJ) isolated from rat hearts in presence of the protease inhibitor phenylmethylsulfonylfluoride (PMSF) contain a Mr 44,000 to 47,000 major polypeptide and have a urea-resistant layer of fuzz on their cytoplasmic surfaces, whereas junctions isolated without PMSF are proteolyzed to a Mr 29,500 polypeptide by a serine protease and have smooth cytoplasmic surfaces (C.K. Manjunath, G.E. Goings & E. Page Am. J. Physiol. 246:H865-H875, 1984). Rat liver GJ isolated with or without PMSF contain a Mr 28,000 polypeptide and have smooth cytoplasmic surfaces. Here we examine the origin, type and inhibitor sensitivity of the heart protease; why similar proteolysis is absent during isolation of rat liver gap junctions; and whether the Mr 44,000 to 47,000 cardiac GJ polypeptide is the precursor of the Mr 29,500 subunit. We show that the Mr 44,000 to 47,000 polypeptide corresponds to the unproteolyzed connexon subunit; that proteolysis of this polypeptide occurs predominantly during exposure to high ionic strength solution (0.6 M KI) which releases serine protease from mast cell granules; that this protease is inhibitable with PMSF and (less completely) soybean trypsin inhibitor and chymostatin; and that in vivo degranulation of mast cells by injecting rats with compound 48/80 fails to prevent breakdown of cardiac GJ during isolation. The results support the concept that GJ from rat heart and liver differ in protein composition.

Animals↗