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G Gabella

Publications and source records attributed to G Gabella.

At least 37 records · Page 2Linked to original sources
PubMed1995

Complex structure of the common carotid artery of sheep.

BACKGROUND: Mechanical properties of blood vessels are dictated by the vessel wall structure. In many large conduit vessels the tunica media is a sheath of circular musculature and the tunica adventitia a layer of fibrous connective tissue with limited longitudinal extensibility. In contrast, the carotid artery of the sheep displays in each tunica a more complex architecture of muscle and connective tissue. METHODS: Vessels collected from ewes were measured and processed for light microscopy and for transmission electron microscopy. RESULTS: Layers of histologically different materials are found within the tunica intima, media and adventitia. (1) The tunica media is made of circumferentially arranged muscle cells markedly different at different depths. In the innermost third of the media, muscle cells are small and with irregular profiles, the cells are widely separated, and the extracellular material is abundant and composed mainly of elastic fibres. In the outermost third, muscle cells are larger and with more regular profiles, the cells are relatively close to each other and the extracellular material is sparse and consists mainly of collagen fibrils. (2) A small number of fibroblasts is found in all parts of the media amongst the preponderant muscle cells. (3) The intima contains fibroblast-like cells and longitudinally arranged muscle cells. (4) The adventitia contains a thick layer of collagen and elastic fibres; external to this, it displays a conspicuous musculature, made of large bundles of longitudinal muscle. CONCLUSIONS: The carotid artery of the sheep presents in all three coats of its wall features which are at variance from those in the better known vessels of small laboratory animals. The presence of many layers of material within the wall, the heterogeneity of the tissues found, and the occurrence of an extensive longitudinal musculature, have important effects on the mechanical properties of the vessel.

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PubMed1995

The structural relations between nerve fibres and muscle cells in the urinary bladder of the rat.

Intramuscular nerve fibres in the bladder of adult female rats were investigated by means of serial sections. The following observations were made. (1) Upon penetrating into the musculature the nerve bundles branch repeatedly, and almost all turn into single fibres; their axons become varicose, the Schwann cell sheath is attenuated, incomplete or absent, and the separation between axonal membrane and muscle cell membrane is reduced to tens of nanometres. (2) All single axons, and some of those within bundles, are varicose, but the characteristic of being varicose is expressed by degrees, and is not an all-or-none state. (3) Varicosities contain vesicles (mostly of the agranular type), microtubules (with little connection with the axolemma or the vesicles), some neurofilaments (scarce or absent in the best developed varicosities), mitochondria (whose size is on average smaller than those of the perikaryon, and a minute amount of endoplasmic reticulum. (4) Terminal varicosities, the true anatomical ending of an axon, are often devoid of Schwann cell sheath, are packed with vesicles, rarely contain microtubules or neurofilaments, and lie close to a muscle cell: the gap is often reduced to approximately 10 nm. (5) Schwann cells accompany the axons within the muscle strands. Unlike the area of the axonal profiles, the area of glial sheath changes little along the length of the nerve fibre, except towards its end. (6) The Schwann cell sheath around a varicosity is often incomplete; the area of the axolemma thus exposed is covered by the basal lamina, and is here referred to as a 'window'. While some varicosities have a window only a few tens of nanometres in width, others have more than one window, and some are devoid of Schwann cell altogether, so that their entire axolemma is in contact with the basal lamina. The Schwann cell never extends beyond the axon, whereas very often (and possibly always) the axon extends beyond the Schwann cell. (7) Intervaricose segments vary in length and diameter, the narrowest ones accompanying the more clear-cut varicosities. Some intervaricose segments are as small as 50 nm in diameter, contain a single microtubule and lack a Schwann cell sheath. Others, sheathed by a Schwann cell, contain a single neurofilament or no organelles at all.(ABSTRACT TRUNCATED AT 400 WORDS)

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PubMed1994

Reversal of muscle hypertrophy in the rat urinary bladder after removal of urethral obstruction.

We studied the ultrastructure of the bladder musculature after first inducing hypertrophy by means of urethral obstruction and subsequently removing the obstruction. With hypertrophy the bladder musculature increases ten-fold or more in volume; after de-obstruction approximately 4/5 of the hypertrophic muscle weight and volume is lost within six weeks. In spite of this very large decrease in muscle mass there is no degeneration of muscle cells or nerve endings or of other cell types in the de-obstructed bladder either at 5 days or at 6 weeks. The individual muscle cells are smaller in size than in the hypertrophic bladder but still larger than control muscle cells. The decrease in muscle cell size is more substantial than the decrease in muscle cell surface. There are no lysosomes or other signs of intracellular degradation in any cells of the muscle layer. The musculature contains a very large amount of intercellular material, mainly collagen. This study documents the great plasticity of the musculature in the reduction of muscle mass after de-obstruction. However, some of the fine structural features are almost as different from the controls as in the hypertrophic muscle.

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PubMed1993

Effect of decentralization or contralateral ganglionectomy on obstruction-induced hypertrophy of rat urinary bladder muscle and pelvic ganglion.

After urethral obstruction the musculature of the rat urinary bladder undergoes extensive hypertrophy, irrespective of whether its innervation is intact or whether one of the two pelvic ganglia has been decentralized or excised. Even the excision of both ganglia does not inhibit muscle hypertrophy. The presence of nerves is not a prerequisite for the muscle growth to occur. The stimulus for growth resides in the bladder itself, and the present and previous observations are in agreement with the notion that the distension of the muscle is a primary stimulus for muscle growth. With bladder hypertrophy, the pelvic ganglion neurons undergo hypertrophy, even when they are devoid of their preganglionic input. Synaptic connection with the preganglionic fibres and stimuli from the spinal cord are not prerequisites for neuronal hypertrophy. However, the hypertrophy is less marked in the decentralized ganglion neurons than in the neurons of the contralateral intact ganglion. With bladder hypertrophy and contralateral ganglionectomy, the neuronal hypertrophy is greater than with either procedure alone, suggesting that the two forms of neuronal growth stimulation can be added to each other.

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PubMed1993

Effects of unilateral pelvic ganglionectomy on urinary bladder function in the male rat.

Micturition interval and micturition volume were measured in water loaded male rats before and up to 6 weeks after unilateral pelvic ganglionectomy. There was no effect on micturition interval until 7 days after the ganglionectomy. Micturition interval then remained increased. Maximal micturition volume was higher than in the control group from 4 to 14 days after surgery. Cystometrograms were recorded 12 days or 6 weeks after surgery. At 12 days the micturition pressure was lower in the unilaterally ganglionectomized than in the controls. After 6 weeks there was no significant difference in micturition pressure. A reduction of micturition pressure by about 50% was observed after i.v. injection of atropine, but no residual urine developed. Electron microscope investigation showed a considerable decrease in number of nerve terminals on the ganglionectomized side 3 days after surgery. Most of them were devoid of synaptic vesicles. On the contralateral side the majority of nerve terminals appeared normal, but many had a decreased number of vesicles. After 14 days the number of terminals was still lower than normal on the ganglionectomized side. They generally contained only a small number of vesicles. Also, on the contralateral side some nerve endings with the reduced complement of vesicles were found. We suggest that the effects of unilateral ganglionectomy on micturition volume and interval can be explained by a decreased sensory input from the bladder and that the effect on micturition pressure is due to a transient decrease in number and function of motor nerve terminals in the detrusor muscle.

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PubMed1992

Hypertrophy and reversal of hypertrophy in rat pelvic ganglion neurons.

An experimental procedure which chronically reduces the lumen of the urethra in adult female rats produced distension of the bladder and conspicuous thickening of its wall, resulting within 6-8 weeks in a ten-fold increase in muscle weight (muscle hypertrophy). During this process, the neurons in the pelvic ganglion that innervate the bladder undergo a large increase in size (neuronal hypertrophy). The average neuronal volume increased by 83%; small neurons became less numerous and large neurons became more numerous than in controls, but there was no increase in the maximum neuronal size. Six weeks after re-operation and removal of the urethral obstruction, the weight of the bladder was reduced (although not quite to the control levels), while the average neuronal size reversed to values very close to controls. In separate experiments, the pelvic ganglion of one side was removed. The nerve fibres in the hemidenervated bladder sprouted, grew and spread to innervate the whole bladder. The neurons in the surviving pelvic ganglion hypertrophied, the average cell volume increasing by 50% in seven weeks. The experiments showed that: (i) the pelvic neurons of adult rats are capable of very extensive growth when the tissue they innervate (bladder muscle) undergoes hypertrophy; (ii) the neuronal hypertrophy is reversible. This was taken to imply that there are factors within the bladder, including trophic substances, that regulate nerve cell volume not only by inducing growth but also by inducing the opposite effect, a cell size reduction; (iii) unilateral ganglionectomy, which did not induce muscle hypertrophy but doubled the amount of muscle innervated by the contralateral ganglion, was followed by marked neuronal hypertrophy.

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PubMed1992

Liquid flow across the epithelium of the artificially perfused lung of fetal and postnatal sheep.

1. The lungs of five fetal (133-140 days gestation) and thirty-four postnatal (2-240 days) sheep were artificially perfused in situ with warmed and oxygenated sheep blood. In postnatal animals the airspace of the lung was filled with liquid similar in composition to fetal lung liquid. In fetal and postnatal animals luminal liquid volume was measured by the impermeant tracer technique. 2. Under resting conditions the pulmonary epithelium of fetal animals secreted liquid at a mean (+/- S.E.M.) rate of 2.0 (+/- 0.4) ml (kg body weight)-1 h-1, those of postnantal animals absorbed liquid at -1.8 (+/- 0.2) ml (kg body weight)-1 h-1. 3. Addition of 2,4-dinitrophenol to achieve a concentration of 1.5 x 10(-3) M in the perfusing blood in postnatal animals caused complete cessation of liquid absorption. 4. Light and electron microscopic examination of the lung after periods of up to 6 h of artificial perfusion showed no evidence of epithelial damage. From 3 h onwards, liquid accumulation was evident in the perivascular spaces. 5. Addition of adrenaline to the perfusate in fetal animals caused absorption of liquid to occur at a mean rate of -2.9 (+/- 1.3) ml (kg body weight)-1 h-1. In postnatal animals adrenaline caused the rate of liquid absorption to increase from a mean rate of -1.4 (+/- 0.2) to -2.2 (+/- 0.3) ml (kg body weight)-1 h-1. 6. In the fetus addition of amiloride (0.8 x 10(-4) M) to the luminal fluid blocked adrenaline-induced liquid absorption and caused secretion to occur at 1.3 (+/- 0.3) ml (kg body weight)-1 h-1. 7. In postnatal animals the response to amiloride was age dependent. In newborn lambs (2-14 days) amiloride blocked liquid absorption and caused secretion of liquid to occur in seven out of eight animals at a mean rate of 0.9 (+/- 0.3) ml (kg body weight)-1 h-1 (n = 8). In older animals (15-240 days) the characteristic response to amiloride was slowing of the rate of liquid absorption (mean rate of absorption,-0.2 (+/- 0.09) ml (kg body weight)-1 h-1, n = 18) with liquid secretion being seen in only three of eighteen animals.(ABSTRACT TRUNCATED AT 400 WORDS)

2,4-Dinitrophenol↗
PubMed1992

The interface between epithelium and lamina propria in the rat urinary bladder.

We investigated by transmission and scanning election microscopy the interface between the epithelium and lamina propria in the rat urinary bladder. A digestion technique that dissolves the basal laminae and collagen fibrils was effective in cleaving the mucosa at this level; the specimens were then prepared for scanning electron microscopy, thus visualizing the basal epithelial surface and the uppermost surface of the lamina propria. The underside of the epithelium is scored by very numerous grooves which in the intact organ are occupied by a dense network of blood capillaries. These vascular grooves allow a large number of capillaries (epithelial capillaries) to run at a distance of a few tenths of a micron from the epithelium. On the side of the lamina propria, after collagen and other extracellular materials had been removed, the capillary network itself is visible in the uppermost region. The network is complementary to that of vascular grooves. Other smaller grooves on the basal surface of the epithelium correspond to nerve fibres which run within a few tenths of a micron from the epithelium.

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PubMed1991

Ultrastructure of the tracheal muscle in developing, adult and ageing guinea-pigs.

The musculature of the trachea of adult guinea-pigs is ultrastructurally similar to other visceral muscles. However, tracheal muscle cells have irregular outlines, large accumulations of glycogen, a small number of gap junctions, and many small elastic fibres and collagen fibrils (50 nm in diameter). Fibroblasts, mast cells, Schwann cells and axons are found within the muscle, but no interstitial cells. Capillaries run in the connective tissue septa. The tracheal muscle is well differentiated at the end of the fetal life. At this time, muscle cells have an appearance similar to that of a mature muscle. However, the cells are smaller, especially in length, and their orientation is less regular. There are no undifferentiated cells; a few muscle cells are seen in mitosis. There is a limited amount of stroma, mainly small collagen fibrils not exceeding 30 nm in diameter. Within the muscle there are many nerves, but no fibroblasts or mast cells. Many structural contacts link together the muscle cells, but there are no gap junctions. Gap junctions develop in the first few days after birth and are distinct in 5-day-old animals. In ageing guinea-pigs (30-36 months old) the muscle cells are slightly larger than in the young adult. They display deep invaginations of the cell membrane and a very irregular profile. There is an increase in the number of glycogen granule clusters, and the basal lamina is particularly prominent. The amount of stroma has increased, and is made of large elastic fibres and collagen fibrils up to 105 nm in diameter.

Aging↗
PubMed1991

Afferent nerve endings in the tracheal muscle of guinea-pigs and rats.

The trachea of guinea-pigs was stained as a whole-mount preparation with the zinc iodide-osmium technique. A distinct class of nerve endings was observed associated with the tracheal muscle. The endings, issued from myelinated fibres of the vagus nerve via the recurrent laryngeal nerve, are distributed on either side of the midline and ventral to the tips of cartilages. They are interpreted as afferent nerve endings that may correspond to slow adapting stretch receptors identified by physiological studies. Each nerve contributes predominantly, but not exclusively, to the receptors of the ipsilateral side. There are 120-180 receptors along the full length of the guinea-pig trachea, their density being higher at the cranial end. The receptors are variable in size and structural complexity, and, to some extent, also in spatial orientation, but distinct subtypes are not recognizable. Receptors of similar morphology and distribution are found also in the rat trachea. The receptors can also be visualized with a cytochrome oxidase method for nerve endings, but they do not stain with immunohistochemistry for the neuropeptides substance P, calcitonin gene-related peptide, vasointestinal polypeptide and neurotensin.

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PubMed1991

A vascular network closely linked to the epithelium of the urinary bladder of the rat.

Scanning electron microscopy was used on the mucosa of the rat urinary bladder after digestion with strong alkali and microdissection. The underside of the epithelium (and the plane of the epithelium-tunica propria interface) is not smooth but is scored by grooves--10 microns wide and 3-4 microns deep--connected into a fine mesh. A net of blood capillaries located in the uppermost part of the tunica propria occupies these grooves. They measure 3-9 microns in diameter, are separated from the epithelium by a gap of 0.3 micron, often show fenestrations, and are accompanied by numerous and extensive pericytes and by some fibroblasts. We discuss these observations in the light of current knowledge of blood flow in the bladder, contraction and distension of the bladder wall and formation of mucosal folds, transport of solutes through the epithelium, and plasma extravasation from mucosal blood vessels in neurogenic inflammation.

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PubMed1991

Nerve fibres in the uterine artery increase in number in pregnant guinea-pigs.

Perivascular nerves of the uterine artery were studied in four-month-old pregnant and non-pregnant guinea-pigs. In pregnancy, the uterine artery hypertrophies (more than two-fold growth in diameter and length and 50% increase in wall thickness), but its density of innervation remains high, because of the growth of many new axons. The axons in a complete transverse section of the vessel increase by 40%. The nerve bundles grow by 100%. Small nerve bundles increase more than large bundles: nearly 70% of the nerve bundles contain 10 or fewer axons in pregnant guinea-pigs (37% in non-pregnant animals). The increase in axon number is accompanied by formation of new varicosities, hence presumably of new neuromuscular junctions.

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PubMed1990

Hypertrophy of visceral smooth muscle.

Smooth muscles of viscera undergo a large increase in volume when there is a chronic, partial obstruction impairing the flow of lumenal contents. Hypertrophy of smooth muscle occurs in various medical conditions and several methods are available for inducing it experimentally in laboratory animals, especially in urinary bladder, small intestine and ureter. The hypertrophic response differs somewhat with the type of organ, the animal species, the age of the subject, and the experimental procedure. Ten- to fifteen-fold increases in muscle volume develop within a few weeks in the urinary bladder or the ileum of adult animals, a growth that would not have occurred in the lifespan of the animal without the experimental intervention. The general architecture of the muscle and the boundaries with adjacent tissues are well preserved. In intestinal hypertrophy, muscle cells increase in number: mitoses are found in mature, fully differentiated muscle cells. Cell division by full longitudinal splitting of muscle cells may also occur. Enlargement of muscle cells accounts for most of the muscle hypertrophy. The hypertrophic muscle cell has an irregular profile with deep indentations of the cell membrane, bearing caveolae and dense bands; however, the cell surface grows less than the cell volume (reduction of surface-to-volume ratio). The nucleus is crenated and is much less enlarged than the cell (reduction of the nucleo-plasmatic ratio). Mitochondria grow in number but in some muscles their spatial density decreases; intermediate filaments increase more than myofilaments. The spatial density of sarcoplasmic reticulum is generally increased. In the hypertrophic intestine, gap junctions increase in number and size; in the bladder, gap junctions are absent both in control and in hypertrophy. Thus the hypertrophic muscle cell is not only larger than a control cell, but has a different pattern of its structural components. Extensive neo-angiogenesis maintains a good blood supply to the hypertrophic muscle. The density of innervation is much decreased in the hypertrophic intestine, whereas it appears well maintained in the bladder. Neuronal enlargement is found in the intramural ganglia of the intestine and in the pelvic ganglion. The mechanisms involved in hypertrophic growth are unknown. Three possible factors, mechanical factors, especially stretch, altered nerve discharge, and trophic factors are discussed.

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PubMed1990

Intramural neurons in the urinary bladder of the guinea-pig.

The urinary bladder of adult female guinea-pigs was stained histochemically to detect the presence of intramural ganglion neurons. Counts on whole-mount preparations of entire bladders revealed the presence of 2000-2500 neurons per bladder, either as individual nerve cells or, more often, as ganglia containing up to 40 neurons. Both ganglia and single neurons lie along nerve trunks and are interconnected to form a plexus. Ganglia occur in every part of the bladder; they are more numerous on the dorsal than on the ventral wall, and they are especially abundant in an area within a radius of 800 microns from the point of entry into the bladder wall of ureters and urinary arteries. The ganglia are located inside the muscle coat and close to muscle bundles; they usually lie nearer the mucosa than the serosa. Ultrastructurally, each ganglion is surrounded by a capsule; in addition to neurons and glial cells, the ganglia contain capillaries, collagen fibrils and fibroblasts; ganglion neurons are individually wrapped by glial cells and are separated from one another by connective tissue.

Animals↗
PubMed1990

Some parasympathetic neurons in the guinea-pig heart express aspects of the catecholaminergic phenotype in vivo.

In a histochemical study of intrinsic cardiac ganglia of the guinea-pig in whole-mount preparations, it was found that some 70-80% of the neurons express aspects of the catecholaminergic phenotype. These neurons have an uptake mechanism for L-DOPA, and contain the enzymes for converting L-DOPA (but not D-DOPA) to dopamine and noradrenaline, i.e. aromatic L-aminoacid decarboxylase and dopamine beta-hydroxylase. Monoamine oxidase is also present within some of the neurons. In these respects, the neurons resemble noradrenergic neurons of sympathetic ganglia, so we refer to them as intrinsic cardiac amine-handling neurons. However, these neurons do not contain tyrosine hydroxylase and show little or no histochemically detectable uptake of alpha-methyldopa, dopamine or noradrenaline, even after depletion of endogenous stores of amines by pre-treatment with reserpine. Noradrenergic fibres from the sympathetic chain form pericellular baskets around nerve cell bodies. The uptake of L-DOPA into nerve cell bodies is not prevented by treatment with 6-hydroxydopamine sufficient to cause transmitter-depletion or degeneration of the extrinsic noradrenergic fibres. Such degeneration experiments suggest that axons of the amine-handling neurons project to cardiac muscle, blood vessels and other intrinsic neurons. The cardiac neurons do not show any immunohistochemically detectable serotonergic characteristics; there is no evidence for uptake of the precursors L-tryptophan and 5-hydroxytryptophan or 5-HT itself, whereas the extrinsic noradrenergic nerve fibres within the ganglia can take up 5-HT when it is applied in high concentrations.

Animals↗
PubMed1990

Urinary bladder of rat: fine structure of normal and hypertrophic musculature.

The fine structure of the muscle of the urinary bladder in female rats is similar to that of other visceral muscles, although it is arranged in bundles of variable length, cross-section and orientation, forming a meshwork. When distended, the musculature is 100-120 microns thick, with some variation and occasional discontinuity. Extended areas of cell-to-cell apposition with uniform intercellular space occur between muscle cells, whereas attachment plaques for mechanical coupling are less common than in other visceral muscles. There are no gap junctions between muscle cells. Many bundles of microfilaments and small elastic fibres run between the muscle cells. After chronic partial obstruction of the urethra, the bladder enlarges and is about 15 times heavier, but has the same shape as in controls; the growth is mainly accounted for by muscle hypertrophy. The outer surface of the hypertrophic bladder is increased 6-fold over the controls; the muscle is increased 3-fold in thickness, and is more compact. Mitoses are not found, but there is a massive increase in muscle cell size. There is a modest decrease in percentage volume of mitochondria, an increase in sarcoplasmic reticulum, and no appreciable change in the pattern of myofilaments. Gap junctions between hypertrophic muscle cells are virtually absent. Intramuscular nerve fibres and vesicle-containing varicosities appear as common in the hypertrophic muscle as in controls. There is no infiltration of the muscle by connective tissue and no significant occurrence of muscle cell death.

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PubMed1989

Some intrinsic neurons of the guinea-pig heart contain substance P.

Whole-mount preparations of the posterior wall of the atria of the guinea pig heart containing intrinsic ganglion cells and nerve plexuses were stained for substance P-like immunoreactivity by the peroxidase-antiperoxidase method. Substance P-like nerve fibres are present as pericellular baskets around most, but not all, of the neuronal cell bodies, and are also found in the connecting nerve bundles, as perivascular nerve plexuses and in the myocardium and pericardium. The majority of ganglion cell bodies are negative for substance P, as reported previously, but we describe for the first time, a small subpopulation of intrinsic neuronal cell bodies which show immunoreactivity for substance P. Therefore, not all cardiac substance P nerves are extrinsic afferent fibres. At present, the physiological role of intrinsic substance P neurones is not clear.

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