Muscle Coat Research Articles

Ultrastructural demonstration of abnormal multiaxonal Schwann-cell units in Hirschsprung's disease

The pathophysiology of Hirschsprung's disease is not fully understood. Using light microscopy we have previously demonstrated the absence of a unique Schwann-cell antigen in the circular muscle of aganglionic colon identified by D7 monoclonal antibody. In an attempt to characterise the morphological changes in neuronal cells at subcellular level, we studied innervation patterns in normal and aganglionic colon by electron microscopy. The most striking observation on ultrastructural serial examination of the entire resected specimen of colon from patients with Hirschsprung's disease was the presence of grossly swollen monoaxonal or oligoaxonal Schwann cell units with loss of cellular contents in the circular muscle of aganglionic colon. The extent of subcellular changes in Schwann cells and axons corresponded with a diminution of immunoreactivity with a panel of neuronal cell antibodies. These ultrastructural findings suggest that degenerative changes in Schwann cells and axons within the circular muscle coat of aganglionic segment may be a significant factor in the pathogenesis of Hirschsprung's disease.

Light and electronmicroscopy of the bowel in an unusual form of Hirschsprung's disease.

In a histological and histochemical study of multiple biopsies of unaffected segments of the bowel from 15 patients with Hirschsprung's Disease (H.D.), the AChE or non-specific esterase and the NADPH tetrazolium reductase enzyme reactions proved to be useful in identification of myenteric plexus islands; and acid phosphatase for the delineation of individual neurones. In the affected segment (usually aganglionic), this myenteric plexus tissue was not reactive for esterase, but individual nerve fibres among muscle fibres of the two muscle coats showed the enzyme product in a third of the cases. Fine structural study of biopsies from a typical case of H.D., showed normal looking axons and Schwann cytoplasm with terminals bearing both andrenergic and cholinergic vesicles in the unaffected colon, smooth muscle fibres with normal fine structure in all parts of the bowel, and loss of neurons with myenteric plexus replaced by nerve fibre groups in the affected rectosigmoid. One patient clinically presenting as a case of severe H.D., with histologically and histochemically normal myenteric and submucous ganglion cells, and not responding to resection of the bowel, showed degeneration of the unmyelinated axons with prominent Schwann cytoplasm, depleted cholinergic but persistent adrenergic vesicles, and markedly thinned and degenerating smooth muscle fibres and myofilaments, suggesting either a primary disorder of muscle tissue of the colon or, less likely, a denervation atrophy with secondary degeneration of the smooth muscle fibres.

ROLE OF THE VAS DEFERENS IN THE FORMATION OF THE SPERMATOPHORE OF THE CRAYFISH (CHERAX)

ABSTRACT The vas deferens of the crayfish Cherax albidus can be divided structurally and functionally into proximal, middle, and distal regions. In cross sections, the vas deferens is comprised of secretory epithelium surrounded by connective tissue and circular striated muscle. The muscle coat thickens around the distal vas deferens, where it is used to extrude spermatophores for transfer to the female during mating. The lumen of the vas deferens contains the spermatophore in various stages of development. Sperm entering the thin proximal vas deferens are supported in a matrix which becomes surrounded by the primary spermatophore layer during transit through the proximal segment. The primary spermatophore layer condenses from secretory products released at the apex of the epithelium by both apocrine and exocytotic mechanisms. The sperm mass and surrounding primary spermatophore layer form a sperm cord which becomes highly convoluted upon passing into the middle vas deferens. The middle vas deferens also begins secreting the secondary spermatophore layer. This layer is comprised of a low density matrix and large and small electron-dense granules. The final synthesis and secretion of the secondary spermatophore layer occurs in the distal vas deferens, which also functions in storing the mature spermatophore. The components of the secondary spermatophore layer are released from the epithelial cells by both aprocrine and exocytotic mechanisms. The secondary spermatophore layer becomes cohesive and relatively insoluble during passage through the distal vas deferens.

Carcinoma of the gallbladder. A clinicopathology of 103 patients and a newly proposed staging.

Tissue samples from 103 patients with gallbladder carcinoma were examined, using 5-mm stepwise tissue sections. Three pathologic stages were used: Stage I; carcinoma invading not further than the muscle coat of the gallbladder, with or without extension along Rokitansky-Aschoff sinuses in the subserosa (11 cases); Stage II, carcinoma extending to the subserosal fibroadipose tissue of the gallbladder (73 cases); and Stage III: carcinoma invading the adjacent organs such as the duodenum, liver, and colon (19 cases). In the 11 patients with Stage I carcinoma, there was no apparent lymph node metastasis and all remained well for 3 months to 14 years after the initial operation. The cumulative 3-year survival rate of Stage I (100%) was significantly higher than of Stage II (40%) and Stage III (10%) (P less than 0.01, P less than 0.001). The Stage I tumors, therefore, can be defined as early carcinoma of the gallbladder. Dysplastic epithelium was seen in the mucosa adjacent to the malignant lesion in 57% of those with gallbladder carcinoma: 73% in Stage I, 59% in Stage II, and 42% in Stage III. Nine gallbladders had multiple foci of adenocarcinoma in a background of a diffuse dysplasia. Immunohistochemical study for carcinoembryonic antigen and carbohydrate antigen 19-9 resulted in positive staining of the dysplastic epithelial element adjacent to the invasive carcinoma and, in a similar fashion, in the carcinoma itself, thereby indicating a close relation between the epithelial dysplasia and adenocarcinoma of the gallbladder.

Comparative morphometric evaluation of the muscle coat of arteries and their functional state

Comparative morphometric evaluation of the muscle coat of arteries and their functional state

Immunohistochemical evidence for the presence of calcium-binding proteins in enteric neurons.

Immunoreactivity for vitamin D-dependent calcium-binding protein (CaBP) has been localized in nerve cell bodies and nerve fibres in the gastrointestinal tracts of guinea-pig, rat and man. CaBP immunoreactivity was found in a high proportion of nerve cell bodies of the myenteric plexus, particularly in the small intestine. It was also found in submucous neurons of the small and large intestines. Immunoreactive nerve fibres were numerous in the myenteric ganglia, and were also common in the submucous ganglia and in the intestinal mucosa. Immunoreactive fibres were rare in the circular and longitudinal muscle coats. In the myenteric ganglia of the guinea-pig small intestine the immunoreactivity is restricted to one class of nerve cell bodies, type-II neurons of Dogiel, which display calcium action potentials in their cell bodies. These neurons were also immunoreactive with antibodies to spot 35 protein, a calcium-binding protein from the cerebellum. From the distribution of their terminals and the electrophysiological properties of these neurons it is suggested they might be sensory neurons, or perhaps interneurons. The discovery of CaBP in restricted sub-groups of enteric neurons may provide an important key for the analysis of their functions.

New observations on the pathogenesis of multiple intestinal atresias

It has been suggested that multiple intestinal atresias result from multiple ischemic infarctions of the intestinal tract. We have studied surgical material from 59 neonates with intestinal atresias seen at our hospital between 1975 and 1986. Forty (68%) patients had single intestinal atresias and 19 (32%) had multiple atresias. There were seven cases of hereditary multiple atresias seen in three families and 12 cases of nonhereditary multiple atresias. All hereditary cases had numerous type I or type II gastrointestinal atresias but none had type IIIa atresia. Six of the seven hereditary cases had multiple atresias in the small as well as large bowel. The 12 patients with nonhereditary atresias had various types of atresias but mesenteric or intestinal interruption was observed in only two patients. All patients with hereditary multiple intestinal atresias showed identical microscopic appearances in the small and large intestine, consisting of sieve-like multiple lumina, each surrounded by its own mucosa and muscularis mucosae but sharing a common muscle coat. There was no evidence of lanugo, bile pigments, or squames within the lumen distal to atretic segments in any of these patients. Six nonhereditary cases who had multiple septal atresias affecting only the small bowel demonstrated essentially similar lesions on microscopic examination as seen in hereditary cases. There was no evidence of arterial occlusion in the mesentery and lanugo, bile pigments, and squames could not be found distally in the intestinal contents in any of these cases. These pathologic findings suggest that all cases of hereditary multiple intestinal atresias and some cases of nonhereditary multiple intestinal atresias are a consequence of a malformative process of the gastrointestinal tract rather than an ischemic process.

Acute ureteric dilatation for ureteroscopy. An experimental study.

The effects of three methods of acute ureteric dilatation (by graded Teflon dilators, low and high pressure balloon dilators) were evaluated radiologically, renographically and histologically in minipigs. The minipig ureter was dilated from its normal calibre of 4 F to 10 F. All three methods caused upper urinary tract dilatation and an obstructive nephropathy which had not resolved 96 h after dilatation. Histology at 24 h showed destruction of the transitional epithelium, with inflammation throughout the ureteric wall. Four weeks after dilatation the ureter was still dilated and urothelial nests were seen in the lamina propria and in the muscle coats. There was no evidence of ischaemic necrosis or ureteric stricture formation. The implications of these findings for clinical practice are discussed.

A Pathophysiological Study of 10 Cases of Hypoxic Cor Pulmonale

A pathophysiological study of the pulmonary vasculature in 10 patients with hypoxic cor pulmonale and severe airways obstruction (five treated and five untreated with long-term oxygen) is presented. The media of muscular pulmonary arteries was normal or atrophic but, in the intima, there was active deposition of longitudinal muscle, fibrosis and elastosis. In the arterioles a medical coat of circular smooth muscle bounded by a new internal elastic lamina had developed, while there was deposition of longitudinal muscle and fibrosis in the intima. In five cases the lumen was subdivided into parallel tubes, found by serial section to lead into alveolar capillaries. These features are distinctive of hypoxaemia and obstructive airways disease. Changes continued until death. The conspicuous longitudinal muscle may be attributable to stretching of vessels round distorted terminal airways; further exploration into mechanisms is required. The hypothesis that vascular changes follow hypoxic vasoconstriction is no longer tenable. No correlations were found between quantitative pathological findings and arterial blood gas tensions, pulmonary artery pressure or haematocrit. There were no differences between patients treated or not treated with oxygen which might suggest that it arrests pathological changes. Thus, once a patient is given oxygen, survival probably depends as much on progressive mechanical changes in the lung as on continuing hypoxaemia.

Scanning electron microscopy of the muscle coat of the guinea-pig small intestine.

We have studied the layers of the muscular coat of the guinea-pig small intestine after enzymatic and chemical removal of extracellular connective tissue. The cells of the longitudinal muscle layer are wider, have rougher surfaces, more finger-like processes and more complex terminations, but fewer intercellular junctions than cells in the circular muscle layer. A special layer of wide, flat cells with a dense innervation exists at the inner margin of the circular muscle layer, facing the submucosa. The ganglia of the myenteric and submucosal plexuses are covered by a smooth basal lamina, a delicate feltwork of collagen fibrils, and innumerable connective tissue cells. The neuronal and glial cell processes at the surface of ganglia form an interlocking mosaic, which is loosely packed in newborn and young animals, but becomes tightly packed in adults. The arrangement of glial cells becomes progressively looser along finer nerve bundles. Single varicose nerve fibres are rarely exposed, but multiaxonal bundles are common. Fibroblast-like cells of characteristic shape and orientation are found in the serosa; around nerve ganglia; in the intermuscular connective tissue layer and in the circular muscle, where they bridge nerve bundles and muscle cells; at the submucosal face of the special, flattened inner circular muscle layer; and in the submucosa. Some of these fibroblast-like cells correspond to interstitial cells of Cajal. Other structures readily visualized by scanning electron microscopy are blood and lymphatic vessels and their periendothelial cells. The relationship of cellular elements to connective tissue was studied with three different preparative procedures: (1) freeze-cracked specimens of intact, undigested intestine; (2) 'stretch preparations' of longitudinal muscle with adhering myenteric plexus; (3) sheets of submucosal collagen bundles from which all cellular elements had been removed by prolonged detergent extraction.

Pharmacology of the coronary circulation

Until recently, the medical management of coronary artery disease consisted of depressing the heart's requirements for oxygen. Little thought was directed towards improving coronary blood flow as it was believed that atherosclerotic lesions were fixed, unchangeable obstructions. Attempts at pharmacological coronary dilatation were, therefore, considered futile. Within the last few years, these concepts have undergone radical revision.t-3 It is now recognized that coronary stenoses are not fixed but are capable of both dilatation and constriction and these changes can have dramatic effects on blood supply to the heart. Drugs that either dilate or prevent constriction of atherosclerotic coronary articles arc, therefore, of value in patients with coronary artery disease. 4,5 However, paradoxically, drugs that dilate distal intramyocardial coronary arterioles may have the opposite effect. Coronary arteriolar dilatation, in the presence of epicardial atherosclerosis, may exacerbate maldistribution of cornnary blood flow and lead to ischaemia. 2'3'6 This confusing picture is best understood by considering the composition of the coronary vascular system. The coronary circulation consists of large proximal coronary arteries that branch and ultimately form an intramyocardial network of small arteries and arterioles. 2-47 The arterioles become smaller metarterioles and they eventually form the capillary bed. Blood returns via the coronary venous system. There are major functional differences between the large proximal coronary arteries and the smaller downstream arterioles. The proximal coronary arteries are large bore, relatively thin-walled vessels that lie predominantly on the epieardial surface of the heart. The:so vessels serve to conduct blood from the aorta to the intramyocardial network of arterioles. They are transport vessels 2-'t,7 and contribute little to the overall vascular resistance of the coronary system. They possess considerable reserve capacity and even when blood flow is maximal, such as during extreme exertion, they continue to conduct the much increased flow of blood without imposing resistance. It is these vessels which are visualized during coronary angiography, undergo coronary atheroselerosis and are bypassed during coronary artery_ surgery. Distal, downstream to the epicardial coronary arteries is a system of smaller arteries, arterioles and metarterioles that end in precapillary sphincters. T M These vessels penetrate throughout the myocardium and are responsible for delivery of blood to the cardiac tissue and for appropriate distribution of blood flow within the myocardlum. They are relatively thick-walled, having a thick smooth muscle coat. At rest, in normal man, blood flow to the left ventricle is about 60 to 80 ml/100 g myocardium/minute. 7 When myocardial oxygen requirements increase, the resistance vessels dilate and permit myocardial flow to increase in proportion to demand. When oxygen requirements decrease, arterioles constrict and limit flow. For example, the subendocardium has a high metabolic rate yet coronary flow is restricted during systole because of a throttling effect of myocardial contraction on intramyocardial vessels, s However, during diastole, subendocardial resistance vessels dilate and blood flow to this region is enhanced and transmural flow is distributed equitably. In this way, intramyocardial vascular tone modulates a tight coupling between oxygen requirements and oxygen supply. Factors responsible for regulating arteriolar tone are not known, but adenosine and other products of metabolism such as potassium ions have ready access to the intramyocardial vessels and are thought to have a regulator role. 9'~~ Epicardial coronary arteries, in contrast, do not participate to any marked extent in flow autoregulation. Even at maximum blood flow rates (mammalian hearts are capable of a six-fold increase in coronary flow), the vessels are of sufficient calibre to permit flow without imposing significant resistance. However, it does appear that some variation in tone occurs and regulatory mechanisms exist. Coronary adrenergic alpha receptors ~* and beta I and beta2 receptors .2 have been identified and serotinergic and neuropeptidergic nerve fibres have been found in mammalian epicardial vessels.t3'*4 Also, high bloodflow states are thought to promote the release of vasodilators from the epicardial vascular endothelium, t s,*s In addition, epicardial arteries are passively dilated when arterial pressure is elevated by manoeuvres such as exercise. Atheroselerosis impairs the function of this perfusion system. Atherosclerosis involves only the epicardial vessels, not downstream resistance arterioles, t7 Now the previously low-resistance epieardial transport arteries take

The Effects of Vasectomy on the Autonomic Innervation of the Human Vas Deferens

Neurohistochemical and fine structural techniques have been employed to examine the intramural autonomic innervation of the human vas deferens following surgical division of the duct one to 15years previously. Samples from sites on the distal (testicular) and proximal (urethral) aspects of the original vasectomy have been compared with control specimens obtained at vasectomy as to the arrangement and distribution of autonomic nerves. In contrast with tissue from the proximal part and from controls, the distal samples revealed a marked reduction in the noradrenergic innervation of the muscle coat. In addition acetylcholinesterase-containing nerves associated with the basal aspect of the epithelium were usually absent from the distal portion of the vas deferens. These findings have been considered in relation to the contractile and secretory activities of the organ following vasovasostomy and may be of importance to the maturation and fertility of spermatozoa.

Autoradiographic study on the distribution of vagal afferent nerve fibers in the gastroduodenal wall of the rabbit

Following unilateral supranodose vagotomy which eliminated vagal efferent fibers, [ 3H]leucine was injected into the ipsilateral nodose ganglion of the rabbit, which was allowed to survive for 10 days. Autoradiographic examination of the distribution of vagal afferent fibers in the gastroduodenal wall revealed many nerve bundles of labeled afferent fibers present in the subserous plexus between the serosa and the muscle coat, where they branched and descended into the muscle coat. Some of the fibers appeared to interact with some myenteric neurons and muscle fibers in a manner suggesting that the afferent fibers may make synaptic contact with the enteric neurons and innervate or attach to the muscle fibers. Furthermore, the afferent fibers were observed in the submucosal plexus between the muscle coat and the muscularis mucosae. In the mucosa the afferent nerve branched in filaments containing one or several afferent fibers extending from the muscularis mucosae through the mucous lamina propria and to the mucous membrane composed of epithelial cells. It was speculated that the afferent fibers terminated as free endings near the mucous membrane.

Finite Element Model of Heat Transfer in the Bovine Part 1: Theory

ABSTRACT A transient, polar coordinate (two-dimensional) finite element model of the bovine body is described. The model includes the core, muscle, fat, skin and hair coat components. The model simulates heat transfer due to conduction and convective blood flow within the animal and by convection, radiation and evaporative cooling from the hair coat. Internal metabolic heat generation, shivering and respiration are also included. Theoretical details of the model are emphasized in this paper..

Distribution of the muscle coat at the omasoabomasal junction and its vicinity in cattle.

Detailed studies on the distribution of the muscle coat at the omasoabomasal junction in cattle, especially in the pila omasi, were carried out in order to clarify the mechanism of closing of the ostium omasoabomasicum. Anatomical and histological observations revealed that the muscle coat forming the circumference of the ostium omasoabomasicum is composed of inner circular and outer longitudinal layers. The former was particularly thickened at the end of the sulcus omasi (pila omasi). Joined to the pila omasi was a thick muscle bundle which extended from the labium sinistrum (left lip) of the sulcus reticuli and ran obliquely along the floor of the sulcus omasi. Moreover, on the abomasal side of the ostium omasoabomasicum, vela abomasi were formed in such a manner as to surround the ostium omasoabomasicum. These were continuous with the edges of the sulcus omasi. Judging from its location and muscular structure, the pila omasi may contract in accordance with the contraction of the reticulum. As a result, the ostium omasoabomasicum may be narrowed and the vela abomasi pulled toward the omasum, perhaps obstructing the ostium omasoabomasicum. Accordingly, it is presumed that the retention of contents in the omasum may effectively prevent abomasal contents from moving backward into the omasum.

The distribution of noradrenergic nerves in the human lower urinary tract.

Noradrenergic nerves have been demonstrated amongst the ganglion cells of the vesical plexus and of the bladder. Trigonal smooth muscle receives a supply of noradrenergic fibres although similar nerves are rarely observed in relation to the smooth muscle of the detrusor. In the male numerous noradrenergic nerves occur in the walls of the bladder neck, prostate, seminal vesicles and vas deferens; nerves of this type are scarce in the smooth muscle coat of the female bladder neck and urethra. The striated muscle of the rhabdosphincter in both sexes receives a scant (but significant) supply of noradrenergic nerve fibres.

Reproduction in the male honey possum (Tarsipes rostratus: Marsupialia): the epididymis.

The epididymis of the adult honey possum, Tarsipes rostratus, is enclosed by a heavily pigmented tunica vaginalis and lies with the testis in a prominent prepenile scrotum. It is connected to the testis by a single ductus efferentis and is lined by approximately equal numbers of cuboidal ciliated and principal cells. It is unusual for marsupials in having no well-defined compartments or fibrous septae and in having extensive convolutions of the duct only at the caudal flexure. Three principal functional zones (initial, middle, and terminal segments) were identified in the epididymis, based on epithelial type and ultrastructural evidence of sperm maturation. Luminal diameter increases progressively throughout the tract, and epithelial height variations (from about 2 to 20 microns) are greatest in the terminal segment. The epithelium itself is remarkably low (maximum of 21.6 microns) compared with that seen in the epididymis of other mammals. The thickness of the peritubular smooth muscle coat increases close to the junction of the epididymis and ductus deferens. Sperm concentrations were estimated from counts of sperm nuclei and thus can be no more than approximations. The figures are consistent, however, with a rapid increase in concentration in the initial segment, indicating extensive fluid resorption. Sperm concentrations appear to peak in the distal zone of the terminal segment, although sampling problems and wide variations in count make such a conclusion only tentative. Principal and basal cells are the predominant cell types in the epididymal epithelium. Basal cells are most abundant in the initial and distal middle segment. Principal cells show structural evidence of active exchange with the luminal contents and have abundant apical stereocilia, the structure of which depends on the epididymal zone. Other cell types occur less commonly in the epithelium. Lipid-rich and phagocytic principal cells are restricted to the middle and distal zones of the middle segment, respectively. Clear cells, restricted to the terminal segment, and halo cells were found in very low numbers. As in some other marsupials, principal cells (possibly specialized for this function) selectively remove cytoplasmic droplets and probably other cellular debris from the luminal contents. In Tarsipes, however, this process is not very efficient, and many discarded droplets pass through to the terminal segment where they form large masses of debris associated with aggregates of degenerating spermatozoa.

The strictures, sinuses, and fissures of Crohn's disease.

One hundred forty-six consecutive specimens of excised bowel from patients with Crohn's disease were studied to determine the relationships between strictures, sinuses, and "fissures." A significant coincidence of sinuses and strictures was observed and sinuses tended to arise proximal to the point of maximal stricture. "Fissures," defined as blind-ending inflammatory tracts that did not penetrate through the full thickness of the muscle coat, were of two types. One type was associated with submucosal fibromuscular hyperplasia and repair and appeared to be an early sinus. The second type was in dilated ileum or colon in the bases of ulcers and is designated an "acute fissure." The anatomic findings suggest that both sinuses and fissures may be due to mechanical factors including intraluminal pressure rather than to any intrinsic quality of the inflammatory process in Crohn's disease.

The Dukes Classification of Colorectal Cancer

To the Editor.— In MEDICAL NEWS & PERSPECTIVES in the May 16 issue, Charles Marwick1accurately refers to the original 1929 article wherein Dr Cuthbert Dukes proposed a classification system for rectal cancer2: A cases, in which the tumor had extended into the submucosa, but not into the muscle coat; B cases, in which the tumor had extended into muscle coat but not into perirectal tissue; and C cases, in which the tumor had extended into perirectal tissue. B cases were further subdivided into Bl, in which the circular muscle was the limit of growth, and B2, in which the longitudinal muscle was reached. C cases were also subdivided into those without lymph node metastasis (C1) and those with lymph node metastasis (C2). Three years later, in 1932, Dr Dukes3abandoned his 1929 original classification and proposed the A, B, C classification (A, limited to rectal wall;

Regional effects of hypoxia and hypothermia on rebound excitation in large intestine of piebald mouse model for Hirschsprung's disease.

Effects of hypoxia and hypothermia on the poststimulus rebound contractile response (PSRR) were studied in the circular muscle coat of the large intestine of the piebald mouse model for Hirschsprung's disease. The PSRR in the terminal segment of the normal large intestine, which corresponds to the aganglionic segment of the piebald mice, was found to be much more resistant to hypoxia than more proximal regions of the bowel. Effects of hypoxia on the PSRR of megacolonic preparations from piebald mice were essentially the same as for the proximal and midcolon of normal mice. The exception was an increase in latency for the PSRR in the intestine of diseased animals that did not occur in the preparations from normal littermates. Effects of hypothermia, unlike hypoxia, were not markedly different in the proximal and distal large intestine. The latency and duration of the PSRR were increased during hypothermia while the amplitude decreased in all ganglionated regions of large intestinal preparations from both piebald mice and their normal siblings. This was interpreted to result from suppression of inhibitory neuronal activity. The results suggest that the capacity for anerobic metabolism within the neuromuscular apparatus responsible for the PSRR is greater in the terminal large intestine than in the proximal and midcolon.