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Biomedical subjects

G Gabella

Publications and source records attributed to G Gabella.

At least 91 records · Page 5Linked to original sources
PubMed1980

Relation between cell length and force production in urinary bladder smooth muscle.

Guinea-pig and rabbit urinary bladders were fixed in glutaraldehyde at different volumes. Strips were dissected out, embedded and cut for phase contrast and electron microscopy. Muscle wall thickness decreased with increased bladder volume as did the radial number of muscle cells. Cell length, measured by a morphometric method increased linearly with bladder radius, indicating that no slippage between the muscle cells occurred. Number of cells per mm2 cross sectional area increased linearly with bladder radius. Volume-active force relations were obtained by pelvic nerve stimulations of guinea pig bladders filled to different volumes. Maximum pressure was obtained at 0.15 ml bladder volume, and maximum wall tension at a volume of 2.5 ml which corresponds to a cell length of 400 micrometers and a cell packing density of about 107 000 x mm-2. Estimation of the length-active tension curve for the average muscle cell in the guinea-pig bladder indicated a maximum active force of 5.5 microN/cell. Maximum active force per cm2 muscle bundle was calculated to be about 59 N. No compensation for extracellular space and nonmuscular tissue within the muscle bundle was made.

Animals↗
PubMed1979

Hypertrophic smooth muscle. III. Increase in number and size of gap junctions.

The smooth muscle cells of the circular musculature of the guinea pig ileum are connected by gap junctions (nexuses) which occupy about 0.21% of the cell surface. When the muscle hypertrophies in the portions of the ileum oral to an experimental stenosis, the muscle cells increase in size and number. Gap junctions become markedly larger than in control muscles and occupy 0.49% of the cell surface. While the cells double their surface area, the number of nexuses per unit surface remains unchanged (47--48 per 1000 microns2). The packing density of intramembrane particles (or pits) in the nexuses of hypertrophic muscle cells is 6700 . microns-2, which is slightly less than in control muscle cells (7200 . microns-2). A characteristic grouping of the particles (or the pits) within the nexus is often observed. Nexuses between two processes originating from the same cell are common. Nexuses do not occur in the longitudinal muscle.

Animals↗
PubMed1979

Hypertrophic smooth muscle. IV. Myofilaments, intermediate filaments and some mechanical properties.

The ultrastructure of filaments is studied in the hypertrophic musculature of the small intestine of the guinea pig oral to an experimental stenosis. No structural change is observed in the thin and the thick myofilaments. However, there is a remarkable and consistent increase in the number of intermediate (10 nm) filaments; they are the predominant type of filament in many hypertrophic muscle cells. Experiments, in which the force developed in vitro by strips of control and hypertrophic musculature upon stimulation with carbachol, indicate that the force per unit sectional area is slightly less in the hypertrophic muscle than in the control tissue.

Animals↗
PubMed1979

Hypertrophic smooth muscle. I. Size and shape of cells, occurrence of mitoses.

An extensive hypertrophy of the muscle coat develops in the small intestine of the guinea pig oral to an experimental stenosis. The profiles of smooth muscle cells become larger and irregular in shape. From the analysis of serial sections the arrangement of the muscle cells is less orderly than in control muscles. Many muscle cells are split into two or more branches over part of their length. The average cell volume is 3--4 times that of control muscle cells; the cell surface increases less dramatically and, in spite of the appearance of deep invaginations of the cell membrane, the surface-to-volume ratio falls from 1.4 to 0.8. The average cell length is only slightly increased compared with controls. Smooth muscle cells in mitosis are observed in all the hypertrophic muscles examined, in both muscle layers; in the circular musculature they occur mainly found in the middle part of the layer.

Animals↗
PubMed1979

Hypertrophic smooth muscle. II. Sarcoplasmic reticulum, caveolae and mitochondria.

The cytological features of hypertrophic smooth muscle cells are investigated in the small intestine of the guinea pig in which a hypertrophy is induced by an experimental stenosis. By freeze-fracture the cell membrane appears richer in intramembrane particles than that of control muscle cells, whereas the number of caveolae per unit surface of cell membrane shows little or no change (16--19 caveolae micron-2). In the sarcoplasm there is a conspicuous increase of both smooth and rough sarcoplasmic reticulum; extent was measured by surface and by volume. Unusual forms of reticulum also appear. Mitochondria are reduced (in percentage volume) to about half the control value.

Animals↗
PubMed1979

Nexuses between the smooth muscle cells of the guinea-pig ileum.

The circular musculature of the guinea-pig ileum has been studied by freeze-fracture to analyze quantitatively the gap junctions (nexuses) between its smooth muscle cells. The average cell surface area and cell volume are 5,074 micron 2 and 3,260 micron 3. The packing density of nexuses is 48/1,000 micron 2 of cell surface or approximately 244/muscle cell. Nexuses range in area from less than 0.1 to approximately 1.5 micron 2 and they occupy 0.212% of the cell surface. The average packing density of intramembrane particles or pits in nexuses is approximately 7,200/micron 2 of nexal surface, indicating that there may be approximately 77,000 intercellular channels in the full complement of nexuses of one muscle cell.

Animals↗
PubMed1978

Effect of stretch and contraction on caveolae of smooth muscle cells.

The number of caveolae present at the surface of smooth muscle cells of guinea-pig taenia coli and visualized by freeze-fracture is about 35 per micron2. (By comparison, endothelial cells of intramuscular capillaries have about 73 caveolae per micron2). The packing density of smooth muscle caveolae is not significantly different in muscle strips isotonically contracted with carbachol or stretched and relaxed in a calcium-free solution, under a range of loads varying from 1 to 15 g. Also the diameter of the fractured necks of the caveolae appears unchanged in all the experimental conditions tested. The plasma membrane of smooth muscle cells often shows a ring of intramembranous particles rimming the opening of a caveola; on the other hand, particles are rare in the membrane of the caveolae themselves. The close relation between caveolae and sarcoplasmic reticulum is readily visualized in freeze-fracture preparations. Characteristic changes of the cell surface shape accompany the contraction and relaxation of the muscle. On rare occasions small aggregates of intramembranous particles are found and it is possible that they represent punctate gap junctions. However, the characteristic clusters of particles found in the circular musculature of the caecum and ileum are not seen in taenia coli.

Animals↗
PubMed1977

Arrangement of smooth muscle cells and intramuscular septa in the taenia coli.

Bands of electron-dense material beneath the cell membrane of smooth muscle cells of the guinea-pig taenia coli provide attachment to thin myofilaments and to intermediate (10nm) filaments; about 50% of the cell membrane is occupied by dense bands in muscle cells transversely sectioned at the level of their nucleus, and between 50 and 100% in small cell profiles nearer the cell's ends. In addition to the known cell-to-cell junctions (intermediate contacts), more complex apparatuses anchor muscle cells together, either end-to-end or end-to-side of side-to-side. They consist of elaborate folds, invaginations and protrusions accompanied by large amounts of basal lamina material. In the end-to-end anchoring apparatuses numerous finger-like and laminar processes from the two cells interdigitate. Other muscle cells have a star-shaped profile in the last few microns of their length, or show longitudinal invaginations occupied by a thickened basal lamina and occasionally by collagen fibrils. The septa of connective tissue extend only for a few hundred microns along the length of the taenia. In taeniae fixed in condition of mild stretch the muscle cells form an angle of about 5 degrees with the septa. In muscles fixed during isotonic contraction the angle increases to about 29--22 degrees, and in longitudinal sections the muscle cells appear arranged in a herring-bone pattern. The collagen concentration in the taenia coli is 4--6 times greater than in skeletal and cardiac muscles. These various structures are discussed in terms of their possible role in the mechanism of force transmission.

Animals↗
PubMed1977

Degeneration of varicose axons and their phagocytosis by smooth muscle cells.

Intramuscular varicose axons of the guinea-pig vas deferens were studied by electron microscopy after surgical and chemical denervation. The intervaricose segments disappear, and the varicosities become disconnected, spherical in shape and either swollen or more electron-dense. Other varicosities, presumably more advanced degenerative stages, appear as phagosomes in the cytoplasm of Schwann cells and of smooth muscle cells. Smooth muscle cells are extensively involved in the process of elimination of the degenerated nerve varicosities.

Animals↗
PubMed1977

Synthesis of collagen by smooth muscle in the hyertrophic intestine.

During hypertrophy of the small intestine of the guinea-pig at the oral side of an experimental stenosis, the individual intestinal segments do not increase in length but undergo a remarkable increase in weight (up to 7 times that of control segments). Concomitantly an increase in collagen content is found; this is usually larger than the increase in weight, and the concentration of collagen is therefore also increased. This effect is more noticeable in the muscle coat than in the wall as a whole. It is suggested, on the basis of histological observations, that some of this collagen is synthesized by smooth muscle cells.

Animals↗
PubMed1976

The costo-uterine muscle of the guinea-pig: a smooth muscle attaching the uterus to the last rib.

A conspicuous smooth muscle (of transverse sectional area comparable to that of the taenia coli) situated in the suspensorium ovarii and in the ligamentum ovarii proprium of the guinea-pig is described. The muscle is attached to the last rib, it reaches the medial side of the ovary, to which it is loosely attached; it passes beyond the caudal pole of the ovary (from which it receives additional muscle bundles), it approaches the oviduct, passing ventral to it, then it spreads around it and eventually reaches the distal end of the uterus; this muscle (which is here indicated as costo-uterine muscle) is in direct continuation with, or transforms itself into, the longitudinal outer coat of the uterus.

Adnexa Uteri↗
PubMed1976

Effect of collagenase on mechanical activity and fine structure of an intestinal smooth muscle.

The effect of the enzyme collagenase (40-200 units-ml-1) on the spontaneous mechanical activity in vitro and on the fine structure of the activity of the taenia was enhanced both in the isometric and isotonic recordings; after several minutes the muscles became slack or elongated to up to twice their resting lengths. The structural changes were dramatic but a number of muscle cells remained apparently unaltered even with the highest concentration and the longest incubation time (120 minutes). The large variety of structural changes were tentatively grouped into two separate sequences. One sequence involved swelling of the muscle cell, dispersion of the filaments and breaking up of the cell membrane: the thick myofilaments increased considerably in size and became heterogeneous in size and shape, but were still recognizable after disruption of the cell membrane. The other disruptive sequence involved separation of the superficial part of the muscle cell, which became electron-lucent, from the core of the cell where filaments were very densely packed. Few or no changes were observed in non-muscle cells.

Animals↗
PubMed1976

Quantitative morphological study of smooth muscle cells of the guinea-pig taenia coli.

A quantitative study of muscle cells of the guinea-pig taenia coli is reported. Stereological methods were used on electron micrographs and phase contrast micrographs. Smooth muscle cells of taeniae fixed under 1 gram load were about 515 mum long. Muscle cell volume was about 3,500 mum3 and cell surface 5,300 mum2. About 168,000 caveolae were found at the surface of each muscle cell, covering about 29% of its surface. They produced a 73% increase of the cell membrane compared to a smooth-surfaced cell. The ratio surface-to-volume is about 1:0.67 if the geometrical surface is considered, or 1:0.39 if the total surface of the cell membrane (including the caveolae) is considered. Mitochondria constituted 3.5-4% of the cell volume. A few nexuses were observed, both between two muscle cells and between a muscle cell and an interstitial cell. In serial sections septa of connective tissue and groups of muscle cells were found to disappear within few tens of microns or to merge with other septa, and the taenia did not appear to be divided into clear-cut muscle cell bundles. Bundles of smooth muscle cells were seen passing from the taenia to the underlying circular muscle. The transverse sectional area of the taenia ranged between 0.14 and 0.39 mm2; it showed about 526 blood vessels-mm-2.

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