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Biomedical subjects

I L Leknes

Publications and source records attributed to I L Leknes.

At least 19 recordsLinked to original sources
PubMed2005

On the structure of intestine and presence of endocytic cells in the lamina propria of platy and black tetra (Teleostei).

The structure of the intestine in platy (Xiphophorus maculatus) and black tetra (Gymnocorymbus ternetzi) and the capability of cells within the intestinal wall to endocytose intraperitoneally injected horse-spleen ferritin, are described. The intestinal epithelial layer has about the same thickness in both species, but the width of the lamina propria and tunica muscularis in black tetra was only about 1/5 of that in platy. Ferritin was taken up by numerous cells within the lamina propria throughout the entire length of the platy intestine. The uptake was demonstrated as large and strongly coloured intracellular Prussian blue granules in sections treated with acid ferrocyanide. There was no such uptake by the lamina propria in black tetras. We suggest that the high numbers of endocytic cells within the intestinal lamina propria of platies provide a local defence against foreign cells and particles. Such a functional role may to some extent compensate for the lack of an HCl-based defence in the digestive system of this stomach-less species.

Animals↗
PubMed2003

Histological studies on the lymphoid organs in prenatal larvae of platy, Xiphophorus maculatus L (Poeciliidae: Teleostei).

The thymus was very large and tightly packed by lymphocytes in prenatal larvae of platy, Xiphophorus maculatus L., whereas the lymphoid tissues in the spleen and trunk kidney were poorly developed at these stages. We therefore suggest that the specific cellular defence is developed much earlier than the corresponding humoral defence mechanisms in this species.

Animals↗
PubMed2001

Endocytosis of ferritin and hemoglobin by the trabecular endocardium in swordtail, Xiphophorus helleri L. and platy, Xiphophorus maculatus L. (Poecilidae: Teleostei).

The cardiac atrium and ventricle of swordtail, Xiphophorus helleri L. and platy, Xiphophorus maculatus L., are spongious, consisting of muscle trabeculae covered by endocardial cells. The cardiac trabecular endocardium is able to take up and store large amounts of horse-spleen ferritin and bovine hemoglobin from the blood stream. No such uptake was registered in endocardial cells lining the cardiac valves, atrio-ventricular junction and ventriculo-bulbar junction. The trabecular endocardium in these species seems to be unable to accumulate latex beads or bovine myoglobin, cytochrome C and holotransferrin from the blood stream. It is proposed that the trabecular endocardium in these species is able to clear the blood stream of some types of waste macromolecules; i. e. this tissue may have a scavenger function. The present results indicate that the uptake of foreign ferritin in bony fish endocardium can be clearly demonstrated at the light microscopic level in deparaffined sections by means of acid ferrocyanide or Mallory solutions. A similar uptake of hemoglobin is demonstrated by means of Mallory stain.

Animals↗
PubMed1987

Endocytosis of horse-spleen ferritin by bony fish endocardium.

The endocytic uptake of horse-spleen ferritin by the endocardial cells in 2 bony-fish species, Xiphophorus helleri and Pollachius virens, is described. In specimens of X. helleri injected intraperitoneally by a ferritin solution 1/10 h before the sacrifice, the endocardial bristle-coated vesicles, cytoplasmic tubules, and endosomes (smooth vesicles of variable size) contain a number of ferritin particles. These particles are taken up by the bristle-coated vesicles, transferred through the cytoplasmic tubules, and emptied into the endosomes. The latter get more tightly packed by ferritin and increase in size with the time elapsed between the injection and sacrifice. After 9 h, most ferritin-packed endosomes (4 to 6 micron) contain fragments of those inclusion bodies (0.5 to 1.5 micron) which normally occur in the teleostean endocardium, and are therefore regarded as lysosomes. The ferritin-rich lysosomes increase greatly in size with time and display a width of 6 to 12 micron after 28 h. The number of cytoplasmic tubules declines rapidly with time, whereas there is a constant production of new endosomes, which probably are derived from the former. The ferritin particles are not accumulated in the endothelium of the bulbus arteriosus, whereas the hepatic endothelial cells take up some small amounts of ferritin. A similar uptake of ferritin as described above was also observed in the heart of P. virens when perfused by a ferritin solution for 3 h. The present results are discussed and compared with those previously reported for the uptake of ferritin in various tissues in fishes and mammals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Dissociation of muscle cells from the bony fish heart.

A method for dissociating myocardial cells from the bony fish heart is presented. Beating hearts of Pleuronectes platessa were perfused by an aerated medium containing 0.1% collagenase and 0.1% hyaluronidase. After 60 min, the hearts were quite soft and easy to dissociate. The cardiac muscle cells were then collected on Nucleopore membranes, and their surface structure was revealed by scanning electron microscopy.

Animals↗
PubMed1986

Fine structure and endocytic properties of subendothelial macrophages in the bulbus arterious of two bony fish species.

The ultrastructure and endocytic properties of the subendothelial macrophages in the bulbus arteriosus of 2 teleosts, Cichlasoma severum and Xiphophorus helleri, are described. These cells show a diameter of 6 to 10 microns and contain a number of membrane-bound inclusion bodies, which vary greatly in size, shape, and electron density. Frequently, these bodies display myelin figures. Further, in the peripheral part of the cell there regularly occur bristle-coated vesicles. In specimens of X. helleri, injected intraperitoneally by a ferritin solution 20 to 400 h before the sacrifice, the subendothelial macrophages in the bulbus arteriosus contain large, ferritin-packed lysosomes. Similar inclusions were also seen in monocytes in the bulbar lumen. In the bulbus arteriosus of C. severum, there regularly occur mast cells beneath the endothelial lining, whereas the bulbar tissue in X. helleri lacks such cells. The present results are discussed and compared with those reported previously on the fine structure of free macrophages in mammals.

Animals↗
PubMed1986

Ultrastructural and ultrahistochemical studies on the ventral aorta in larvae of a teleost, Poecilia reticulata.

The ultrastructure of the ventral aorta of Poecilia reticulata is described in larvae of variable age. In postnatal larvae this structure is located within the ventral pharyngeal wall. The tunica media consists of elongated smooth muscle cells, surrounded by a network of elastic fibrils (10 to 20 nm). The muscle cells are rich in free and membrane associated ribosomes, and contain a well developed Golgi apparatus surrounded by membrane-bound, electron dense bodies. During the first 21 d of postnatal life, the number of ribosomes declines gradually, whereas there is a corresponding increase in the amount of contractile material. In addition, the number of intercellular, elastic fibrils seems to increase with advancing age. No elastic lamina was seen in the present tissue, but in the 21 d old larvae the subendothelial elastic fibrils are sometimes aligned and may therefore make up an elastic lamina at a later stage of development. Probably, the elastic fibrils are composed of a central string (2-4 nm) of unknown chemical nature, covered by a layer of elastin. Thus, the elastic fibrillar network in young and adult bony-fish may be regarded as heavily reticulose elastin laminae, resembling those of the early fetal aorta in mammals. The present intercellular elastin is shown to be intensely stained with phosphotungstic acid at low pH and may therefore be rich in basic proteins. In 3 mm prenatal larvae the heart and the posterior part of the aorta are located at the outside of the body, whereas the anterior part occurs in the ventral pharyngeal wall. The aortic endothelium and tunica media consist of undifferentiated cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Actin Cytoskeleton↗
PubMed1985

Ultrastructural and ultrahistochemical studies of post-mortem changes and effects of hypoxia in the bony fish heart.

The ultrastructural and ultrahistochemical properties of post-mortem changed and hypoxic heart tissue of Gadus virens, Gadus morhua, and Poecilia reticulata are described. When incubated for 0.5 h at 20 degrees C the cardiac tissue is rich in vacuoles and endocardial blebs. After 1 h of incubation, the myocardial mitochondria contain some amorphous, flocculent densities (50-100 nm), which seem to increase in number and size with advancing incubation time. Furthermore, the mitochondria in heart perfused by a calcium-containing solution for 7 h at hypoxic conditions contain large numbers of highly electron dense annular-granules (35-50 nm). Numerous myocardial mitochondria exclude tannic acid in tissue incubated or perfused for up to 1.5 h, whereas all mitochondria seem permeated by this substance when incubated for 5 h or perfused at hypoxic condition for 7 h. The amount of myocardial glycogen in P. reticulata is greatly reduced in the hypoxic heart compared with the normal heart. The mitochondria and contractile material, however, seem to tolerate oxygen depletion remarkably well. The present results are compared with those reported previously for the post-mortem changes and hypoxic hearts in fishes and mammals.

Animals↗
PubMed1984

Calcium in myocardial tissue and isolated mitochondria from a teleost.

A method is presented for isolating cardiac mitochondria from bony-fish. Calcium levels in ventricular whole tissue and isolated mitochondria of Gadus virens L. are determined by atomic absorption flame spectroscopy, and were found to be about 8 and 16 nmolCa/mg prot., respectively. In conclusion, the calcium concentration within the myocardial mitochondria in this species may be nearly three times higher than at the outside, and probably these structures serve as a "calcium sink". The results are compared with those previously reported for mammals.

Animals↗
PubMed1984

Ultrastructure of bony-fish heart tissue treated with beta-glycerophosphate/lead citrate or adenosine triphosphate/lead nitrate.

The ultrastructure of bony-fish heart tissue is described when subjected to beta-glycerophosphate/lead citrate (9.2 less than or equal to pH less than or equal to 9.4) or adenosine triphosphate/lead nitrate (pH = 7.3). When treated in the former way, electron dense precipitates occur in the endocardial and myocardial endoplasmic/sarcoplasmic reticulum, Golgi apparatus, and nuclear intermembranous space. Such precipitates are absent in the control tissue and reflect therefore probably alkaline phosphatase activity. In tissue treated with adenosine triphosphate/lead nitrate the precipitates are irregularly distributed, and may also occur in the control tissue. In the present material, they therefore seem not to reflect adenosine triphosphatase activity. The results are compared and discussed with those revealed in the present study for the bony-fish intestine and with those previously reported for various mammalian tissues.

Adenosine Triphosphatases↗
PubMed1984

Ultrastructural studies on the heart of bony-fish larvae.

The ultrastructure of the heart in 2 and 6 d old larvae of Melanogrammus aeglefinus and 1, 7, 14, and 21 d old larvae of Poecilia reticulata, is described. Additional studies were done on prenatal specimens of P. reticulata. In the atrium of M. aeglefinus the endocardium is separated from the muscle wall by a wide, electron lucent space, which probably contains cardiac jelly (Davis 1924). The myocardium is an 1 cell-thick layer in the atrium, whereas it consists of 2 to 4 cells in the ventricle. Cardiac trabeculae seem to be absent. The contractile material appears more developed at the endocardial side of the muscle wall than at the epicardial side. Thus, in the latter area the myofibrils are thin, few in number, and embedded in large amounts of free ribosomes. Often they radiate from a spot of electron dense material or an intercalated disc. Generally, intercalated discs, short nexuses and specific heart granules (Jamieson and Palade 1964) occur in ventricular as well as in atrial myocardial tissue. In P. reticulata cardiac jelly seems absent, whereas cardiac trabeculae occur regularly, particularly in the ventricle. The myofibrillar apparatus displays a nearly adult structure. However, in the ventricular wall, there occur spots and bands of intracellular, electron dense material at that sarcolemma facing the subepicardial space. Normally, myofibrils extend from this material into the cellular cytoplasm. Subsarcolemmal electron dense material was only scarcely seen in the atrial wall.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

The effects of post-mortem changes and calcium depletion on the ultrastructure of myocardial cells in a teleost.

The effects of post-mortem changes and calcium depletion on the ultrastructure of myocardial cells in a teleost, Gadus virens L., are described. When incubated at 4 degrees C in cacodylate buffer/Ringer's solution for 8 h some few myocardial cells appear swollen and their mitochondria contain several small (50-250 nm) flocculent densities. In tissue incubated for at least 80 h the mitochondria in all myocardial cells contain a number of such densities. Also, the size of these structures seems to increase with incubation time. Further, after being incubated for at least 150 h the myofibrils appear often twisted and broken, and the electron density of the Z and I bands gradually declines. At prolonged incubation times (about 1,000-1,300 h) the actin filaments and Z band material seem gradually to dissolve, whereas the myosin filaments still make up a distinct A band. Intercalated discs in tissue incubated in calcium-free medium for 4-28 h appear to display a nearly normal structure. The results of the present study are compared with those previously reported for mammals. The observed differences in decomposition rates within teleostean myocardial tissue are discussed.

Animals↗
PubMed1984

Morphometric analysis of myocardial cells in a teleost.

Morphometric parameters are described for myocardial cells in the ventricle and atrium in a teleost, Gadus virens L. The myofibrils volume fractions are 73 and 78% in ventricle and atrium, respectively. The corresponding values for mitochondria and sarcoplasmic reticulum are 23 and 20%, and 0.5 and 0.4%. The muscle cells in the ventricle contain more glycogen than the atrial ones. The morphometric parameters are compared with those previously reported for cardiac muscle cells in mammals.

Animals↗
PubMed1984

Ultrastructure of the parietal pericardium in teleosts.

The ultrastructure of the parietal pericardium in Melanogrammus aeglefinus, Paracheirodon innesi, and Poecilia reticulata is described in larvae of variable age. This structure is composed of a mesothelial layer facing the pericardial cavity and an outer layer of collagen tissue. The latter is continuous with the surrounding tissue, i.e. mainly skeletal muscles. Generally, the parietal pericardium is attached to loose connective tissue dorsally, whereas its ventral and lateral parts are connected to muscles and tendons. Posteriorly, it is fused with the peritoneum. In prenatal larvae of P. reticulata the parietal pericardium is in contact with yolk material. The parietal mesothelial cells are attenuated and contain numerous ribosomes, a well developed Golgi apparatus, and a number of membrane-bound inclusion bodies (0.1-0.4 micron) of moderate electron density. In addition, numerous pinocytotic vesicles (80-100 nm) occur in differentiated mesothelial cells, whereas they are scarce in undifferentiated cells. Furthermore, bristle-coated vesicles are very rare in differentiated mesothelial cells, whereas they are seen regularly in undifferentiated cells. The collagen fibre bundles of the parietal pericardium are often orientated perpendicularly to each other, and in postnatal larvae of P. reticulata a one cell thick layer of melanophores occurs within the fibrous tissue. These cells contain numerous membrane-bound, highly electron-dense inclusion bodies (0.3-0.6 micron). They are occasionally seen in Paracheirodon innesi also, whereas they are absent in 2 and 6 days old larvae of M. aeglefinus and prenatal larvae of P. reticulata. Macrophages, capillaries, and nerve bundles occur in the pericardial and subpericardial connective tissue. The present results are discussed and compared with those previously reported for mammalian parietal pericardium.

Animals↗
PubMed1982

On the ultrastructure of the ventricular endocardium and bulbar endothelium in 3 teleostean species.

The endocardium in the ventricle and the endothelium in the bulbus arteriosus are described in 3 phylogenetically distant teleostean species, Betta splendens, Pistella riddlei, and Xiphophorus maculatus. The ventricular endocardial cells are attenuated and contain a number of bristle-coated vesicles (BCV). In the former 2 species these cells contain numerous ribosomes, a low number of moderately electron dense bodies (MDB) and a poorly developed agranular endoplasmic reticulum (AER). In the latter species, however, these cells are poor in ribosomes, but very rich in MDB and AER. In the species studied the bulbar endothelial cells contain high numbers of ribosomes, whereas BCV and AER are poorla developed. In P. riddlei these cells have a height of 3-7 microns and are closely packed by MBD, whereas in B. splendens and X. maculatus they appear to be flat and contain a very low number of MDB. The results of the present work are compared with those scare findings previously reported for the teleostean ventricular endocardium. The structural differences described may reflect phylogenetical distances.

Animals↗
PubMed1982

Ultrastructural studies on the atrio-ventricular junction and ventriculo-bulbar junction in heart of teleosts.

The ultrastructure of the atrio-ventricular junction (A-V junction) and ventriculo-bulbar junction in the heart of a teleostean species, Gadus virens L., is described. The former junction is a narrow canal having a length of 0.35 to 0.60 mm and a wall thickness of 0.20 to 0.32 mm. At the lumenal side of the junctional wall occurs a layer of myocardial tissue which is in continuity with that of the atrium and ventricle. Further, at the atrial side of the junction this tissue is trabeculated, whereas it is untrabeculated at the ventricular side. A number of nerves occur near the atrium. The myocardial cells are tightly packed into bundles, which are surrounded by a thick external lamina. These cells are connected by numerous nexuses and desmosomes, and are rich in myofibrils. At the atrial side of the A-V junction the endocardial cells contain numerous bristle-coated vesicles, tubules of agranular endoplasmic reticulum and large inclusion bodies of moderate electron density, whereas at the ventricular side these cells are poor in bristle-coated vesicles and agranular endoplasmic reticulum, and the inclusion bodies are small and electron dense. The ventriculo-bulbar junction is a narrow canal; the wall is 0.5 to 1.0 mm thick and contains outermost high amounts of loose collagen tissue, and innermost a layer of dense collagen tissue. Between the 2 latter layers occurs a layer of myocardial tissue which is continuous with that of the ventricle. The endocardial cells in this junction is structurally similar to those located at the ventricular side of the A-V junction. The structure of the A-V junction in teleosts is compared with that of the A-V node and bundle of His in mammals, and the sino-atrial junction in teleosts. It is proposed that the myocardial tissue of the A-V junction in teleosts may conduct electrical impulses between atrium and ventricle.

Animals↗