Fiber type composition of abdominal muscles in Japanese macaques (Macaca fuscata)

The muscle fiber composition and cross-sectional area of muscle fiber types were investigated histochemically in the abdominal muscles (rectus abdominis muscle, obliquus externus abdominis muscle, obliquus internus abdominis muscle and transversus abdominis muscle) of three Japanese macaques (Macaca fuscata). Muscle fibers were classified into three fiber types (Type I, II A and II B) by myosin ATPase activity and succinate dehydrogenase activity. Each abdominal muscle in Japanese macaques contained high proportion of Type II B fibers and there were no large differences in the fiber type composition between the abdominal muscles. The range of mean fiber type percent was 26-32% Type I, 21-22% Type II A, and 46-52% Type II B fibers. Thus, based on the histochemical fiber type composition, the separate abdominal muscles appear to have a similar functional capacity. The cross-sectional area was larger for Type II than for Type I fibers, and the areas were similar in Type II A and Type II B fibers in each muscle. The rectus abdominis showed larger fibers of each type compared to the lateral abdominal muscles. The high proportion of Type II B fibers and large fiber size for Type II B fibers suggest that the abdominal muscles of Japanese macaques have properties similar to the propulsive and locomotory muscles in the limbs.     

Neuronal nicotinic receptor operates slow Ca2+ mobilization at mouse muscle endplate

The authors describe the anatomical characteristics of the levator labii superioris muscle by dissection in cadavers. PURPOSE: We describe the characteristics of these muscle, the details and relations, hopefully contributing to the study of muscle of the face. METHODS: Twenty faces of cadavers were dissected. The following features were studied: origin, insertion, length, width, thickness, relations, innervation and blood supply. RESULTS: In all cases the muscle originated from the inferior orbital margin. Two insertions were observed: via lateral fibers, superficial to the orbicularis oris muscle and via deep fibers than form part of the raphe at the corner of the mouth (70%); via superficial fibers to the orbicularis oris muscle (30%). The average of the length was 24.66 mm and the average of the thickness was 3.57mm. The width at its insertion was 11.2mm, and at the origin was 15.96mm. The levator labii superioris muscle was found to be anterior to the levator anguli oris; it was posterior to the distal portion of the zygomaticus minor (90%) and posterior to the mid portion of the zygomaticus minor (10%). The innervation was from the inferior branch of the zygomatic nerve (facial nerve) and from the infraorbital nerve (trigeminal nerve). The inferior portion of the muscle is supplied by branches of the angular artery and the superior part from branches of the infraorbital artery.     

Dermatomyofibroma (Plaquef?rmige Dermale Fibromatose)

We reported a patient with dermatomyofibroma and reviewed the literature to characterize the immunohistochemical features of dermatomyofibroma. A 25-year-old woman presented with an asymptomatic, well-circumscribed, red-brown plaque on the left posterior shoulder. Microscopic examination revealed a non-encapsulated but well-circumscribed tumor in the mid-dermis extending into the upper subcutaneous fatty tissue. The tumor was composed of faintly eosinophilic, thin, wavy collagen fibers arranged as intersecting fascicles with an arrangement predominantly parallel to the skin surface. Embedded among the wavy fibers, there were a fair number of nuclei that were elongated, vesicular, and uniform in size. Immunohistochemical studies using a peroxidase-antiperoxidase technique disclosed that the cytoplasm of the tumor cells was positive for muscle actin. The tumor cells were negative for alpha-smooth muscle actin, desmin, factor XIIIa, S-100 protein, and CD34. Clinical, histopathologic, and immunohistochemical analysis confirmed dermatomyofibroma.     

Distribution of GABA immunoreactivity in the central and peripheral nervous system of amphioxus (Branchiostoma lanceolatum Pallas)

On the basis of labeling with an anti-gamma-aminobutyric acid (GABA) antibody, we report for the first time the presence and distribution of GABA-immunoreactive cells in the central and peripheral nervous system of amphioxus. In the nerve cord, there is a large dorsorostral group of cerebrospinal-fluid-contacting (CSFc) cells at the caudal end of the brain vesicle that gives rise to a large ventral commissure and neuropilar region. In the middle and caudal region of the brain, numerous commissural and CSFc neurons are situated below the region of large dorsal cells. In the spinal cord, several types of GABA-immunoreactive neurons of different size, appearance, and distribution were observed. In the dorsalmost region, very small commissural cells are scattered regularly along the cord. More ventrally in the cord, GABAergic neurons, both of commissural and CSFc cell types, form segmental groups, but scattered cells are observed throughout. These cells give rise to dense longitudinal fascicles of GABAergic fibers and to scattered commissural fibers. The caudal ampulla lacks GABAergic cells and fibers. Some of the fibers of the most rostral and caudal peripheral (sensory) nerves, as well as some sensory cells of the rostral and caudal epidermis, are GABA immunoreactive. The significance of these results for the understanding of the evolution of GABAergic systems of vertebrates is discussed.     

Regeneration of adrenal cortical tissue after adrenal autotransplantation

OBJECTIVE: This study examined the muscle fiber type distribution within the normal adult levator veli palatini muscle. METHODS: Levator veli palatini muscle tissue was harvested from the palates of 12 (seven female, five male) adult noncleft cadavers. Adjacent sections were stained for adenosine triphosphatase at pH 10.4 or 4.2. After mounting, magnifying, and photographing, Type I versus Type II fiber types were differentiated by the intensity of, or by the inhibition of, staining of matched fibers at each pH level. Type I fibers stained light at pH 10.4 and dark at pH 4.2, while Type II fibers stained light at pH 4.2 and dark at pH 10.4. MAIN OUTCOME MEASURES: The number of fibers counted for each specimen ranged from 60 to 616. The numbers of Type I and Type II stained fibers appearing in each muscle tissue sample were determined and expressed as a percentage of the total number of fibers identified. A few identified fibers could not be labelled as either Type I or Type II. RESULTS: The overall proportion of Type I fibers, averaged across all specimens, was 59.8%. Male specimens had 67.4% Type I fibers and 31.8% Type II fibers, while female specimens had 54.4% Type I fibers and 44.4% Type II fibers. CONCLUSIONS: Observed fiber type distributions were similar to those reported for other articulatory muscles, but differed slightly from previously reported distributions for normal levator veli palatini. The distributions observed in this study provide a baseline against which to relate fiber type data from the levator veli palatini of cleft palates to the functional status of the velopharyngeal mechanism.     

Conformational transitions provoked by organic solvents in beta-lactoglobulin: can a molten globule like intermediate be induced by the decrease in dielectric constant?

The macroscopic arrangement of the termination of the thoracic duct (TD) was examined in detail in Japanese cadavers, and the distribution of various types of collagen, tenascin, laminin, and fibronectin in the framework of the wall of the thoracic duct termination was demonstrated. We identified several branching patterns and pathways of the TD (i.e., those terminating 1) at the venous angle (Type A); 2) at the end of the internal jugular vein (Type B); 3) at the the external jugular vein (Type C); or 4) in a complex with various branches (Type D). The TD often divided into two or three trunks before or after passing beneath the left brachiocephalic vein. Compared with the main trunk of the TD, fewer muscle fibers, elastic fibers, specific compounds of the extracellular matrices, and valvular connective tissues were found near the termination of the TD and the valves of the TD and veins. Smooth muscle cells were arranged irregularly in each region of the TD.     

Quantitative analysis of smooth muscle fibers in corpus cavernosum of human fetuses

PURPOSE: Quantify objectively the normative distribution and the percentage of smooth muscle fibers in the corpus cavernosum of human fetuses with 24 weeks post-conception (WPC) of gestational age. MATERIAL AND METHODS: We studied 7 penises taken from 7 fresh human fetuses. We analyzed 5 randomized sections from each penis and in every section we analyzed 3 fields, totaling 15 fields per penis and 105 fields for the final results. Immunohistological staining for the smooth muscle fibers was used to accentuate the differences between the intracavernous structures (smooth muscle fibers and collagen fibers). The fields studied were digitized with a final magnification of 450X and a computerized analysis of the smooth muscle fibers was performed with image analyzer software. The percentage of smooth muscle fibers per standard square area was estimated and the mean value was used for each penis. RESULTS: The distribution of smooth muscle fibers in the corpus cavernosum of human fetuses with 24 WPC of gestational age ranged from 17.52% to 27.76% of the total area. The mean value was 22.72% and the standard deviation was 3.56. CONCLUSIONS: Our results show that the percentage of smooth muscle cells in corpus cavernosum of human fetuses with 24 WPC of gestational age is significantly smaller when compared with the data available for adult cadavers.     

Differential sensitivity to androgens within a sexually dimorphic muscle of male frogs (Xenopus laevis)

Male frogs use their forelimb flexor muscles to clasp females during the mating behavior known as amplexus. We investigated the effects of testosterone on a principal forelimb flexor, the flexor carpi radialis muscle (FCR), using morphological and histochemical techniques. Male Xenopus laevis were surgically manipulated to produce high or low levels of circulating testosterone for an 8-week period. After this treatment, measurement of fibers in muscle cross-sections revealed that average fiber size was positively correlated with testosterone level. This effect was not the same for all muscle fibers, however. Fibers in the shoulder region were more sensitive to testosterone than fibers in other regions of the muscle. Histochemical staining of cross-sections showed that the patterns of staining for myosin ATPase or succinic dehydrogenase (SDH) were not influenced by testosterone levels, but total SDH activity was increased by testosterone treatment. When sensitivity to testosterone was correlated with ATPase activity, fibers with high ATPase activity were found to be more sensitive to testosterone than fibers with low activity, regardless of position within the muscle. Most fibers with high ATPase activity were located in the shoulder region of the muscle. These fibers are innervated by different motor axons than are fibers in the elbow region of the muscle, and contractions of shoulder (but not elbow) region fibers, elicited by stimulation of motor axons, are slowed by testosterone treatment (Regnier and Herrera, 1993, J. Physiol. 461:565-581).     

A scanning and transmission electron microscopic study of fiber arrangement in the hepatic capsule

The arrangement of fibrous elements in the rat hepatic capsule was examined under a scanning electron microscope (SEM) after alkaline or acid maceration of the serous coat, in conjunction with examination of the thin sections using a transmission electron microscope (TEM). The elastic fibers appeared as thin threads in a densely meshed network, lying just beneath the serous coat. Their surface was granular with short rods in the materials fixed with paraformaldehyde. In contrast, the collagen fibers were observed as relatively thick threads, with fascicles of collagen fibrils that were uniform in size. These fascicles extended in various directions to form rough meshes that were traversed by small fascicles and anastomosed with each other. The fibrous branches of the elastic fibers extended on or into the underlying collagen fibers to be anchored, while the collagen fibers converged on many areas of the liver surface, and were transferred into the interlobular connective tissues. The findings of the present study thus suggest that the fiber arrangement plays an effective role in the mechanical protection of the fragile liver cells and delicate serous cells from pressure and friction damage by the neighboring abdominal organs and walls of the abdominal cavity due to the elastic mobility of the subserosal elastic network in addition to the possible slippery cushion of a serous layer on the serous cells.     

Developmental expression of dystrophin, dystrophin-associated glycoproteins and other membrane cytoskeletal proteins in human skeletal and heart muscle

Dystrophin, utrophin and the dystrophin-associated glycoproteins, beta-dystroglycan and adhalin, were analyzed, together with the membrane cytoskeletal proteins beta-spectrin, vinculin and talin, and adult and fetal myosin heavy chains, in 25 normal human fetuses from 8 to 24 weeks of gestation. Dystrophin was present in heart and skeletal muscle from 8 weeks although in the latter was mainly in the cytoplasm at this stage. Utrophin expression increased until around gestational weeks 19/21, but by 24 weeks immunostaining and immunoblot band intensities had reduced. Beta-dystroglycan was scarce in skeletal muscle at 8 weeks, increased with maturation and was more abundant in heart of the same age. Adhalin appeared later than beta-dystroglycan on skeletal muscle fiber surfaces, positivity became more intense as the fibers matured. In heart adhalin was detectable only in groups of cells at 12-16 weeks. From 8 weeks all fetal myotubes expressed beta-spectrin on their surfaces, while vinculin and talin positivity was mainly at the periphery of the fascicles, increasing with age. Adult slow myosin was seen in most myotubes at 10 weeks. Secondary myotubes then formed which increasingly expressed adult fast myosin, while still retaining fetal myosin. By 24 weeks most fibers expressing adult slow myosin had lost fetal myosin and were more mature in the expression of most membrane proteins. Muscle membrane organization during human fetal development is a complex process and takes place earlier in heart than skeletal muscle.     

The peritoneal free flap: an anatomic study

In view of a possible clinical application of an isolated microvascular peritoneal flap, an anatomic study was performed in order to determine the peritoneal vascular territory of the deep inferior epigastric artery. For this, the deep inferior epigastric artery was injected unilaterally with Araldite in 30 embalmed cadavers and bilaterally with india ink in 15 fresh cadavers. In 70 percent of the embalmed cadavers, a constant pattern of three branches from the deep inferior epigastric artery could be identified. The peritoneal vascular supply is not derived solely from these three branches but also from multiple small branches sprouting directly from the main stem of the deep inferior epigastric artery and from segmental and muscular branches. Therefore, classification of peritoneal branches arising from the deep inferior epigastric artery seems to be of little clinical importance. In all cases, the india ink injected in the deep inferior epigastric artery colored a similar territory of the parietal peritoneum. Considering the magnitude of the peritoneal vascularization by the deep inferior epigastric artery, implementation of an isolated free or pedicled peritoneal flap seems to be possible. Such a microvascular peritoneal flap vascularized by the deep inferior epigastric artery may be used, for example, for reconstruction of mucosal defects in the head and neck region.     

Peripheral nerve disorders--clinical pathological approaches]

Clinical pathological approach is defined as combination of neurological, neurophysiological and neuroradiological findings for the interpretation of the morphology of the sural nerve. For this purpose, first, the usefulness of simultaneous biopsy of sural nerve and ipsilateral short peroneal muscle was presented. This method has helped establish the diagnosis of angitis or amyloidosis in some cases. Furthermore, motor-dominant clinical picture was ascertained by relative preservation of sural nerve in contrast with severe changes in intramuscular nerve fascicles. Second, histochemistry using UEA-1 lectin to detect somatic sensory C fibers was discussed. UEA-1 specifically binds to unmyelinated axons and small neurons in dorsal root ganglia as well as substantia gelatinosa of the spinal cord. Serial semithin and ultrathin sections were obtained. The semithin section was removed of epon and stained histochemically with UEA-1. Positive fibers in the semithin section was compared with the counterpart in the ultrathin sections. UEA-1 positive fibers were found to comprise 20% of all unmyelinated fibers and be randomly distributed among the entire nerve fascicles. The application of this technique to pathological specimens is now undergoing. Third, an autopsy case with sarin intoxication was reported as an example of systemic study of the peripheral nervous system. The patient was a 51-year-old man who inhaled sarin in the attack of Tokyo Subway. He fell into vegetative state and was passively maintained for 13 months. Peripheral sensory nerve showed typical pattern of dying back-type distal peripheral axonopathy. It might be indicated that peripheral nerve be carefully checked among the sarin victims. In conclusion, the aim of our approach is to combine all clinical information, introduce recent advance in neuroscience, and try to find possible cure to intractable neurological disorders.     

Pathological changes induced by PhTx1 from Phoneutria nigriventer spider venom in mouse skeletal muscle in vitro

The 'armed' spider Phoneutria nigriventer is responsible for most human accidents involving spiders in Brazil. The effects of fraction Tx1 (PhTx1) from the venom of this spider were investigated by physiological and morphological methods using the mouse phrenic nerve-diaphragm preparation. PhTx1 (1 and 5 microg) did not affect the twitch tension of muscle fibers under indirect electrical stimulation. At this same concentration, PhTx1 also did not alter the miniature end-plate potential (mepp) frequency and amplitude, nor did it change the resting membrane potential 60 min after addition to the preparation. Light microscopy (LM) revealed that in muscles incubated with PhTx1 a number of fibers were morphologically altered, as evidenced by microvacuolization and myofibril hypercontraction and loss within 15 min after toxin administration. Transmission electron microscopy (TEM) showed sarcoplasmic reticulum swelling, disorganization of the sarcomeres and mitochondrial damage, and occasionally, sarcolemmal discontinuities with a persisting basal membrane. The intra-muscular fascicles of the phrenic nerve showed myelinated axons with vacuolated myelin sheaths as well as peri- and intra-axoplasmic vacuoles. The neuromuscular junction changes were variable, but were rarely severe. Thus, although PhTx1 did not depolarize or hyperpolarize the neuromuscular junction, it was nevertheless toxic to a restricted number of muscle fibers and nerve structures. The site of action of PhTx1 may involve the sarcolemma and axolemma as suggested by the morphological abnormalities which could reflect hydroelectrolytic disturbances.     

Spectral pattern of neonatal cerebral blood flow velocity: comparison with spectra from blood pressure and heart rate

BACKGROUND: Extrafusal muscle fibers of human striated skeletal muscles are known to have a uniform innervation pattern. Motor endplates (MEP) of the "en plaque" type are located near the center of muscle fibers and distributed within the muscles in a narrow band. The aim of this study was to evaluate the innervation pattern of human facial muscles and compare it with that of skeletal muscles. METHODS: Ten facial muscles from 11 human cadavers were dissected, the nerve entrance points located, and the dimensions measured. All muscles were stained in toto for MEPs using Acetylcholinesterase (AChE) and examined under the microscope to determine their location. Single muscle fibers were teased to evaluate the stained MEPs. RESULTS: The length of the different facial muscles varied from 29 to 65 mm, which correlated to the length of the corresponding muscle fibers. MEP zones were found on the muscles in the immediate vicinity of the nerves' entrance points and located eccentrically. Numbers and locations varied from muscle to muscle. Three MEP zone distribution patterns were differentiated: numerous small MEP zones were evenly spread over the muscle, a predominant MEP zone and two to three small zones were spread at random, and two to four MEP zones of equal size were randomly scattered. One MEP of the "en plaque" type was found in 73.8% of the muscle fibers and two to five MEPs were found in 26.2%. The distances between the multiple MEPs on one muscle fiber varied from 10 to 500 microm. CONCLUSIONS: This study suggests that facial muscles differ from skeletal muscles regarding distribution and number of MEPs. The eccentric location of MEP zones and multiple MEPs suggests there is an independent mechanism of neural regulation in the facial muscle system.     

The qualification of different free muscle transplants to reconstruct mimic function: an experimental study in rabbits

With the scutuloauricularis muscle, we developed a new model for experimental free transplantation of mimic muscles in the rabbit and studied the qualification of different muscles for free functional grafting into the position of the facial muscle, which is to be replaced. Forty adult female white New Zealand rabbits were distributed to four groups of 10 rabbits each. In group 1, the operative techniques of the new transplantation models were developed in the scutuloauricularis muscle, the pectoralis descendens muscle, and a comparable part of the rectus femoris muscle. In group 2, the scutuloauricularis muscle was transplanted orthotopically with microneurovascular anastomoses on the left side; in group 3, the pectoralis descendens muscle was transplanted into the position of the scutuloauricularis after its removal; and with the animals in group 4, a piece of the rectus femoris muscle was transplanted into the position of the mimic muscle after its removal. In all muscle transplants, the neurovascular supply was reestablished microsurgically by end-to-end anastomoses to the superficial temporal vessels and direct nerve coaptation to the facial nerve branches supplying originally the scutuloauricularis muscle. Nine months after transplantation, force measurements were performed in all transplanted muscles and the scutuloauricularis muscles of the control side. Cross-sections stained for ATPase after alkaline preincubation at pH 10.4 were used for computer-assisted planimetry of the muscle fibers. The orthotopically transplanted scutuloauricularis muscles reached with 2.84 (+/-1.04) N for maximal tetanic tension on the average 87.7 (+/-32.1) percent of that of the control scutuloauricularis muscles, the pectoralis descendens muscles with 4.25 (+/-2.15) N on the average 188.7 (+/-100.7) percent of that of the controls, and the pieces of rectus femoris muscles 6.62 (+/-2.16) N or 185.3 (+/-45.4) percent of that of the controls. All three muscles were identified as fast contracting muscles before and after transplantation. By transplantation, the content of type II muscle fibers changed from 58.2 to 68.0 percent in the scutuloauricularis muscle, from 62.4 to 74.4 percent in the musculus pectoralis descendens, and from 92.5 to 82.8 percent in the rectus femoris muscle. For the first time, an experimental model for free transplantation of mimic muscles was developed and functionally assessed. The most important result of this study was the fact that the double-sized muscle grafts developed twice the force of the control scutuloauricularis muscles, although reinnervated by the original muscle nerve branch. This result underlines the usefulness of overdimensioning during clinical muscle transplantation. It was also shown that parts of big muscles can be grafted with results similar to those experienced with complete smaller muscles.     

Effects of adrenalectomy or RU-486 on rat muscle fibers during hindlimb suspension

The purpose of this study was to investigate the effects of a glucocorticoid antagonist, RU-486, and of adrenalectomy (ADX) on rat skeletal muscle structural properties after 3, 7, and 14 days of hindlimb suspension (H). After H, a significant loss in muscle weight was observed as early as 3 days in soleus (SOL; -10%) and adductor longus (AL; -14%) muscles. In SOL, after only 7 days, a reduction (-14%) in type I fiber percent distribution occurred, accompanied by an increase (+129%) in intermediate type I fibers. Fiber type changes increased depending on the duration of H. In AL muscle, no change occurred after H in the fiber type composition despite a similar degree of muscle atrophy. Treatment with RU-486 or ADX significantly reduced the loss of SOL weight observed after 14 days (-42 and -44%, respectively, vs. -50% for H rats), delayed the SOL atrophy (from 3 to 7 days), and normalized the shift in fiber type distribution induced by H. In SOL, administration of RU-486 (but not ADX) partly prevented the reduction in size induced by H of all the fibers. In AL, neither treatment affected the extent of muscle atrophy, even though the reduction in type IIa fiber size was prevented by RU-486 but not by ADX after 14 days of suspension. ADX or RU-486 administration did not prevent the extensor digitorum longus weight loss observed after 14 days of suspension but allowed a recovery of its normal fiber type composition.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nitrergic innervation of the rat larynx measured by nitric oxide synthase immunohistochemistry and NADPH-diaphorase histochemistry

We evaluated the involvement of nitric oxide (NO) in the laryngeal innervation of rats using NADPH-diaphorase (NADPH-d) histochemistry and neuronal nitric oxide synthase (nNOS) immunohistochemistry. The findings obtained by NADPH-d histochemistry were identical with those obtained by nNOS immunohistochemistry, indicating that NADPH-d is nNOS in the laryngeal innervation system. We found NADPH-d-positive nerve fibers in every region of the larynx. In the epithelia of the mucosa, a small number of NADPH-d-positive nerve fibers were detected. The plexus of NADPH-d-positive nerve fibers was commonly found in the lamina propria, and some of these fibers were clearly associated with blood vessels. We also noted NADPH-d-positive nerve fibers in the region of laryngeal glands. Some of these fibers appeared to terminate in the glandular cells. We found NADPH-d-positive nerve fibers with varicosities in the intrinsic laryngeal muscle and free-ending nerve fibers on the muscle fiber. Motor end plate-like structures were positive for NADPH-d histochemistry. The NADPH-d-positive nerve fibers appeared to terminate at motor end plate-like structures in two of nine rats examined. A cluster of NADPH-d-positive neurons were occasionally present in the lamina propria of the laryngeal mucosa, in the connective tissue between the thyroid cartilage and intrinsic laryngeal muscle, and in the connective tissue near the cricoarytenoid joint. The present findings suggest that NO participates in the autonomic, sensory, and motor innervation of the larynx.     

The hypomobile temporomandibular joint

The hypomobile (restricted) temporomandibular joint (TMJ) is usually caused by a restricted joint capsule or by an anteriorly displaced disk. Here, painful unilateral hypomobility (19 mm jaw opening), with normal disk position, caused by voluntary immobilization after a dental procedure, was the presenting symptom. Management included inflammation control, TMJ manipulation (mobilization), and lateral pterygoid muscle relaxation. Inflammation and pain were alleviated by nonsteroidal anti-inflammatory drugs (NSAIDs) and local TMJ ice massage. TMJ mobilization was performed at every visit, to tear joint capsule adhesions and to realign collagen fibers. Exercise consisted mainly of resistive opening (the patient resists an upward force applied to the chin), with the jaw maintained at full opening. This produced lateral pterygoid muscle relaxation at full length, aiding in the restoration of a pain-free 44 mm opening.     

Magnetic resonance images in patients with acute traumatic injury of the temporomandibular joint: a preliminary report

Dorschner et al have described the unique function and form of several different muscle systems of the urinary bladder neck. If these systems have different functional responsibilities, then the muscles must undergo different ageing processes, as stated in the theory of function-dependent ageing. One characteristic of histologic ageing is the change over time in the proportion of muscle cells to connective tissue, a phenomenon we have demonstrated in both the ciliary muscle and in the two muscle systems of the small intestine. Using an SIS-Image Analysing System, we have now measured automatically the ratios of muscle cells to connective tissue in sections from several regions of the urinary bladder neck, taken from 50 male and 15 female cadavers. Our results confirm new functional explanations of the different muscle systems in the bladder neck. The relative volume of muscle cells in both the sphincter trigonalis m. and the dilator urethrae m. diminishes continuously with age. In the ejaculatorius m., however, the volume of muscle cells first increases until beginning at the end of the third decade, it decreases until senescence. As was presumed, the proportion of muscle cells in the detrusor vesicae m. does not decline during the later decades. The volume of muscle cells and fibers in both urethral sphincter muscles, however, decreases with age, beginning in early childhood.