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H Engedal

Publications and source records attributed to H Engedal.

At least 37 records · Page 2Linked to original sources
PubMed1982

New temporary pacing lead for use after cardiac operations.

A newly designed temporary pacemaker lead (Medtronic Model 6400), which has a solid defined electrode surface area of 7.5 mm2, was compared with a multifilamental stainless steel electrode in common use (Davis & Geck, DG). Thirty-nine patients had both types of electrodes inserted intramyocardially in the right ventricle. A DG electrode fastened to the pericardium served as a reference lead. In addition to the standard Medtronic 7.5 mm2 electrode (n = 11), specially made Medtronic electrodes with areas of 5 mm2 (n = 10), 10 mm2 (n = 10), or 7.5 mm2 with platinum-iridium tips (n = 8) were studied. Measurements of myocardial stimulation threshold and resistance were made in both electrodes throughout the postoperative period. The patients' electrograms were recorded on magnetic tape for computer analysis of amplitudes and slew rates. The Medtronic 7.5 mm2 electrodes showed overall better results than 5 and 10 mm2 leads. Maximum stimulation threshold on the Medtronic 7.5 mm2 electrodes was medium 3.4 mA versus 10 mA on DG electrodes (p less than 0.001). The tissue resistance on Medtronic 7.5 mm2 was almost double than on the Davis & Geck electrodes (median 311 ohms versus 164 ohms on the day of minimum resistance, p less than 0.001). There were no significant differences in electrogram amplitudes between the two electrode types studied (5.52 versus 4.68 mV, p greater than 0.1), but the slew rates were significantly higher on the Medtronic (0.56 versus 0.37 V/sec; p less than 0.01). The new lead is an important innovation in temporary pacemaker lead design compared to the commonly used multifilamental leads.

Adult↗
PubMed1981

Calcium and magnesium levels in isolated cardiac mitochondria from mice injected with isoproterenol.

Calcium (Ca) and Magnesium (Mg) are determined by atomic absorption flame spectrometry in isolated cardiac mitochondria from mice receiving subcutaneous injections of DL-isoproterenol HCl (ISO), and in mitochondria of untreated controls. In the controls, mitochondria were isolated in the presence or absence of ruthenium red. On the absence of ruthenium red in the isolation medium, mitochondrial Ca levels increase by about 300%, while levels of Mg remain unchanged. Focal myocardial necrosis following a single ISO-injection is shown by electron microscopy. Ca and Mg levels are largely unaffected by a single dose of ISO until 24 h after the injection. A slight increase in Ca occurs in the 48 h samples. When multiple injections of ISO are given every 12th hour of 48 h, 72 h and 96 h, respectively, endogenous Ca and Mg increase significantly. It is suggested that this increase might be associated with ISO-induced cardiac hypertrophy rather than with the pharmacological effects of ISO per se.

Animals↗
PubMed1980

Atrial specific granules of the human auricle in embryogenesis, tissue culture, and hypertrophy.

The ultrastructure of atrial specific granules of the human auricle has been studied in myoblasts of 8-12 week embryos, in myoblasts cultured for 15 days, and in cells of the hypertrophied juvenile and adult atrium. The granules of young myoblasts and those of cultured cells are fairly evenly distributed throughout the sarcoplasm. Myocytes of the hypertrophied juvenile auricle show structural characteristics indicative of granule formation. Structural evidence of exocytosis has not been observed in either of the tissues studied. In the cultured and the hypertrophied tissue the granules are structurally well preserved even in areas with extensive intracellular lysis.

Adult↗
PubMed1980

On the origin of Z-band material and myofilaments in myoblasts from the human atrial wall.

The origin of cardiac myofibrils in cells from the atrial wall in human embryos was studied, Z-band substance appears throughout the cytoplasm as irregular electron dense patches in a network of thin filaments. The thin and thick filaments are synthesized as separate units in the sarcoplasm and are later aggregated into myofibrils. Complexes of Z substance and thin filaments occur numerously at different stages of myofibrillar organisation. Thick filaments are formed in close proximity to free ribosomes and are later incorporated in an hexagonal pattern into the Z-band/thin filament complex.

Cytoplasm↗
PubMed1980

Calcium and magnesium levels in isolated mitochondria from human cardiac biopsies.

A non-enzymatic method is presented for isolating mitochondria from small-sized human cardiac samples, including ventricular needle biopsies of 15-25 mg of wet weight. Electron microscopy demonstrates that these fractions are rich in structurally well preserved mitochondria. Calcium and magnesium levels of fractions are determined by atomic absorption flame spectroscopy. Comparative analyses are made in similar fractions of the mouse ventricle. Calcium concentrations of mitocondria isolated in the presence of ruthenium red do not differ significantly between the human auricle and ventricle, averaging 61 nmol Ca/mg protein and 68 nmol Ca/mg protein, respectively. Mitochondrial calcium level is lower in the mouse ventricular fractions, averaging 7 nmol Ca/mg protein. Mitochondrial magnesium amounts to slightly less than 60% of the calcium levels in the human heart, while it exceeds the calcium level by more than 100 per cent in the mouse heart. There is no significant difference of mitochondrial calcium between normal auricles, and, auricles of patients with increased right atrial mean pressure and/or volume overload.

Adult↗
PubMed1979

Effects of isoproterenol on the dense core and perigranular membrane of atrial specific granules.

Following subcutaneous injections of isoproterenol hydrochloride (ISO), atrial cells present a large number of partly degranulated or completely clear "specific granules" enclosed by an intact membrane. Such profiles were never encountered in normal controls and might suggest ISO-induced release of a secretory product. Permeability of perigranular membrane was tested using the extracellular macromolecular tracer horseradish peroxidase (HRP). Reaction product was entirely absent within granules of atrial cells in which the sarcolemma was made permeable to HRP molecules by the ISO injections. This seemed to be the case even in heavily labelled cells in which the peroxidase had penetrated the mitochondrial membranes. In atrial cells impermeable to the tracer, the specific granules closely apposed to the sarcolemma were always HRP-negative. The release mechanism of a possible secretory substance from the specific granules is discussed.

Animals↗
PubMed1978

The T-tubule system in the myocardia of the sand rat and mouse as demonstrated by horseradish peroxidase.

The transverse tubule (T-tubule) system in papillary muscles of the sand rat and the mouse were studied with the aid of a diffusion tracer (horseradish peroxidase). The T-tubule system in the sand rat showed a typical mammalian pattern with sarcolemmal tubules invaginating at the Z-band level of the sarcomere. These tubules follow a transverse direction in the cell with frequent longitudinal side-branches which connect tubules at different Z-band levels. In the mouse myocardium, the T-tubules also start as lateral invaginations from the sarcolemma at the Z-band levels. In the cell interior, however, the tubules ramify and brake up into a complicated system of spirally running tubules. These spirals, of relative small diameter (400A--700A), frequently expand and form lobulated cisternae at the Z-band levels.

Animals↗
PubMed1978

Calcium in isolated mitochondria from the left ventricular wall.

The content of calcium per mg mitochondrial protein has been measured by conventional biochemical methods in myocardial tissue of some mammalian species. In addition, a method is presented for (1) the analysis of mitochondrial volumes in the same tissues and (2) calculating the amount of calcium in units of 10(6) mitochondria. It appears that a highly significant correlation exists between the calcium content and the number of mitochondria, with a positive correlation coefficient of 0.92. The mean mitochondrial volume in fractions of the rabbit myocardium was found to be 1.3386 micron3. Electron microscopic studies demonstrate pure mitochondrial fractions and only moderate structural alterations. The method described may represent a useful supplement for the estimation of calcium fluxes in mitochondria and of alterations in their volume, number and structure under conditions of myocardial ischemia.

Animals↗
PubMed1978

Ultrastructural studies on the formation of myoflilaments and myofibrils in the human embryonic and adult hypertrophied heart.

The myofibrillogenesis in the human embryonic heart is described. The synthesis of thin filaments, which are the first to appear, takes place in close proximity to smooth surfaced SR tubules. Z-band material is closely related to the thin filaments and appears first as irregularly distributed patches in the filamenteous mass. Further cellular differentiation includes an organization of the thin filaments/Z-band material. The synthesis of thick filaments, which follows that of the thin filaments, takes place in ribosome rich areas of the cell. They are rapidly incorporated into the strings of organized thin filaments/Z-band material. The periodic binding sites on both kinds of filaments are believed to play an important role in the precise ordering of the filaments. The formation of myofilaments in the adult hypertrophied human heart is also described. The similarities between this process and that observed in the embryonic heart are striking, and we believe it to be the same process.

Adult↗
PubMed1978

Substructure of inner mitochondrial membranes of myocardial cells as shown by cryo-ultramicrotomy.

The substructure of the inner mitochondrial membranes has been studied by cryo-ultramicrotomy under conditions during which denaturation of proteins by treatment with chemical solutes has been totally avoided. In such preparations, the inner membrane has a substructure consisting of globular subunits. These subunits have an average diameter of ca. 20 A-ca. 62 A and are fairly regularly spaced. Intracristal space is absent in the unstained, freeze-dried preparations, whereas a space of ca 40 A is seen in preparations lightly treated by OsO4-vapour. It is concluded that the subunits of the inner mitochondrial membranes probably consist either of single protein molecules or of complexes of protein molecules.

Animals↗
PubMed1978

Cardiac hypothermia evaluated by ultrastructural studies in man.

Transmural left ventricular biopsies from 13 patients undergoing cardiopulmonary bypass were studied. The hypertrophic myocardium was protected by deep hypothermia (15 degrees C.) during ischemic arrest for a maximal period of 96 minutes. Biopsies were taken at the start of bypass, at the end of aortic cross-clamping, and after 20 minutes of reperfusion. The structure of the mitochondria remained normal, whereas cellular alterations in the form of widened intercalated discs, interstitial and intracellular edema, myelin figures, and slight myofibrillar lysis were observed in all stages. As no clear correlation between these structural injuries and aortic cross-clamping time was seen, they are a result of cardiac hypertrophy rather than intraoperative ischemia.

Adult↗
PubMed1977

Primary 9 + 0 cilia in the embryonic and the adult human heart.

Primary 9 + 0 cilia have been found in the embryonic and the adult human heart. Proximally the cilia show the typical 9 + 0 filament arrangement. Rearrangement of the filaments occur in their distal regions. The cilia are usually found in deep invaginations of the cell membrane, but can also be found in a superficial position. Close connections are frequently found between cilia and thin cytoplasmic extensions from neighbouring cells.

Adult↗
PubMed1977

Calcium containing particles in mitochondria of heart muscle cells as shown by cryo-ultramicrotomy and X-ray microanalysis.

Mitochondria of normal myocardial cells of the sand rat and the mouse as well as of the left ventricle of man, have been examined for their content of calcium. Ultrahistochemistry and X-ray microanalysis revealed two basically different inclusions: Osmiophilic mitochondrial granules and spherical mitochondrial particles. Osmiophilic mitochondrial granules were found in conventionally fixed and plastic embedded tissues as well as in cryosections of chemically fixed and sucrose infused tissues. Such granules lacked inert electron density and probably consisted mainly of unsaturated lipids. X-ray spectra obtained from these tissues revealed no peaks for calcium. Spherical mitochondrial particles were present in dry-cut cryo-sections of N2-frozen tissues not treated by fixatives and/or cryoprotectants. These particles were deeply electron dense in unstained, freeze-dried cryo-sections. They usually measured from 600 A-900 A in diameter in the normal myocardium of the sand rat and the mouse and from 250 A-400 A in diameter in the left ventricular myocardium of man. Significant calcium peaks could be identified in the X-ray spectra of these particles, whereas none occurred in the analyses of other tissue regions. Potassium was detected with about equal frequency in the particles and in other parts of the tissue. On the basis of the inert electron density of the particles and their absence in chemically fixed tissues as well as of the results of the X-ray analysis, it is concluded that they contain precipitates of extremely labile ions of mitochondrial calcium.

Animals↗
PubMed1977

Preservation of shock-frozen myocardial tissue as shown by cryo-ultramicrotomy and freeze-fracture studies.

Myocardial tissue was quickly quench-frozen by letting the specimen fall either into liquid nitrogen (LN2) or into LN2-slush, or, by drill-propelling the specimen into LN2 at a speed of 1.5 m/s. The preservation of the tissues was studied in ultrathin, dry-cut and freeze-dried cryo-sections. Shock-freezing by propelling into LN2 yields extensive areas of well preserved tissue without hole damage. Quenching into LN2-slush shows variable results, while a maximum of hole damage is obtained by letting the specimen fall into LN2. Replicas of freeze-fractured tissue which had been quench-frozen by the same methods confirmed these observations. By the drill-propelling, areas 2000-5000 micrometer2 wide reveal good preservation without visible ice crystals. Such areas occur within a superficial band of tissue to a depth of c. 20 micrometer. Even at 35 micrometer and 50 micrometer depth good preservation may be registered at the periphery of the replicas. Description is given of modifications in accessories and methods in order to make the LKB CryoKit more suitable as a routine instrument. These modifications cover replacement of the knife coolant container by a coolant brass container in open connection with three copper tubes, replacement of one of the LKB Dewar flasks by a 25 litre Dewar equipped with a Balzers filling device, and replacement of the LKB plastic sleeve fixed to the back of the specimen coolant container, by two perspex-glass discs mounted in the slit between the Ultrotome base and the cryo-chamber. In addition, modified constructions are presented of the grid-carrier, the press-assembly as well as of the container for freeze-drying and warming up of the frozen sections.

Animals↗
PubMed1977

Ultrastructure of abnormal membrane inclusions in nuclei of human myocardial cells.

The ultrastructure of the nuclear envelope was studied in cardiac muscle cells of 12 patients undergoing cardiopulmonary bypass surgery. Two main types of membrane inclusions, globular and tubular, were observed in the nuclei. The globular type was found in 6 patients. The globular inclusions were about 0-5mu to 1-5mu in diameter and lined by two unit membranes equal in structure to that of the nuclear envelope. The lining was probably always in continuity with the nuclear membranes. Such inclusions contained a granular matrix in which no cytoplasmic organelles could be seen, with the exception of a limited number of ribosomes. The tubular type of nuclear inclusion was observed in the cardiac tissue of 3 patients. These tubules ran in straight or slightly bent segments of about 0-2 mu to 1-6 mu length, interrupted by bendings at obtuse or right angles. The diameter of their lumina measured about 300 A to 800 A. Such tubules were nearly always found in areas of the nucleoplasm rich in heterochromatin. Nuclear pore-like structures were occasionally found in the tubular wall. The tubular wall consisted of a single unit membrane shown to be in continuity with the inner membrane of the nuclear envelope. Since these nuclear aberrances have been observed at all of the stages examined, the possibility is considered that they may represent a specific nuclear response to the process of cardiac hypertrophy.

Cardiomegaly↗
PubMed1976

Ultrastructural studies on the growth of filaments and sarcomeres in mechanically overloaded human hearts.

The ultrastructure of myocardial cells was studied in four patients with left ventricular myocardial hypertrophy due to aortic and/or mitral valvular disease. Signs of cellular lysis and synthesis were present in juxtanuclear, interfibrillar, and subsarcolemmal areas. Subsarcolemmal areas contained a granular matrix with foci of polyribosomes, mitochondria, well preserved membranes, a proliferating sarcoplasmic reticulum, and thick and thin filaments and Z-band formations at different stages of development. Z-band substance and thin filaments appeared in the cytoplasm in close proximity to free polyribosomes and endoplasmic membranes and were seemingly not associated with the sarcolemma. These findings were interpreted as evidence for a proteosynthetic activity leading to the formation of new myofibrils and sarcomeres during the chronic stage of hypertrophy. Comparative studies showed that this process has much in common with the genesis of contractile cardiac units in the mammalian embryo. Anomalous Z-band accumulations were studied in normal myocardial cells of various vertebrates and in cells of the overloaded human heart. No evidence of a proteosynthetic activity was detected in the expanded Z-bands.

Adult↗
PubMed1976

Ultrastructure of mitochondria-containining nuclei in human myocardial cells.

The ultrastructure of myocardial cell nuclei was examined in a group of 12 patients undergoing cardiopulmonary bypass surgery. In one patient (aged 60 years) with rheumatic heart disease, myocardial cells were observed which contained mitochondria with well preserved membranes within their nuclei. Such intranuclear mitochondria were observed with equal frequency in all of the three stages examined, i.e. at the start and end of aortic crossclamping and after 20 min of reperfusion. Approximately 2-3% of the total number of nuclei studied in this patient contained mitochondria. A partial disintegration of the membranes of the affected nuclei was sometimes seen. These findings are discussed in relation to the hypothesis of a de novo synthesis of mitochondria inside the nucleus, and also, in relation to the "trapping theory" of mitochondria through the nuclear envelope.

Biopsy↗