Nitric oxide synthase in the external urethral sphincter of the sheep: immunohistochemical and functional study

PURPOSE: We studied the distribution of neuronal nitric oxide synthase (nNOS) and the effects of nitric oxide (NO) modulating drugs on contractile function of the external urethral sphincter of lambs. Gender differences were evaluated. MATERIALS AND METHODS: Longitudinal and transverse sections of the external urethral sphincter from 10 female and 10 male lambs were studied using reduced nicotinamide adenine dinucleotide phosphate-diaphorase histochemistry and nNOS immunocytochemistry. Isometric contractile responses to electrical field stimulation were recorded from external urethral sphincter preparations from 47 female and 45 male lambs and the effects of NO modulating drugs were evaluated. RESULTS: We detected nNOS in the sarcolemma of some but not all striated fibers, where nNOS seems to be concentrated at the neuromuscular junction. In addition, nNOS was present in nerve fibers and intramural ganglia. The density of innervation decreased toward the distal part of the external urethral sphincter and was higher in male preparations. No significant functional effects of the NOS inhibitor NG-nitro-L-arginine (10 mM.) or the NO donors diethylamine and spermine NONOate (Sigma Chemical Co., St. Louis, Missouri) (5 mM. each) on external urethral sphincter isometric contractility were found in either gender. CONCLUSIONS: Despite the evidence for nNOS at the sarcolemma and nerve fibers of the external urethral sphincter the physiological relevance of these immunohistochemical findings remains to be determined.     

Striated muscle fiber compositions of human male urethral rhabdosphincter and levator ani

PURPOSE: We clarified the contractile properties of human male periurethral striated muscle fibers to better understand how the rhabdosphincter and the levator ani maintain urinary continence. MATERIALS AND METHODS: Muscle specimens were obtained from 52 male patients who underwent radical prostatectomy or radical cystectomy. The specimens were frozen in liquid nitrogen. Frozen sections (10 microm thick) were stained with myofibrillar ATPase at different pH values (pH 4.2, 4.6 and 10.6), and evaluated for quantitative parameters and fiber type distribution. Myosin heavy chain analysis was performed using SDS-PAGE. RESULTS: Of all 52 cases 37 provided specimens that could be divided into the 2 major fiber types, type 1 (slow twitch) and type 2 (fast twitch). Although type 1 muscle fibers were predominant in RS and LA muscle groups (RS 69.6 +/- 2.7%, LA 67.0 +/- 2.0%), mean muscle fiber size was significantly smaller in RS (mean area 906 +/- 86 microm(2)) than in LA (mean area 2,967 +/- 170 microm(2)) (p <0.0001). In 11 specimens type 2 muscle fibers could be subdivided into types 2A (fast fatigue resistant) and 2B (fast fatigable). Type 2A fibers were significantly more prevalent than type 2B fibers (p <0.05). Likewise, MHC analysis of these 11 specimens found a significantly higher percentage of fiber type 2A expression products (MHC 2A) than of fiber type 2B expression products (MHC 2X) (p <0.05). CONCLUSIONS: RS and LA contribute to urinary continence mechanism by slow contraction. Moreover, the smaller mean size of muscle fibers in RS suggests more fatigue resistance compared with muscle fibers in LA because small fibers have a shorter diffusion distance for metabolic substrates. These results should help contribute to a more detailed understanding of the function of periurethral striated muscles in the human male.     

Innervation of the female human urethral sphincter: 3D reconstruction of immunohistochemical studies in the fetus

OBJECTIVES: The precise location, origin and nature of nerve fibers innervating the urethral sphincter have not been clearly established. Classical anatomical studies based on cadaver dissections have provided conflicting results concerning the location of pudendal and autonomic nerve fibers. This study was designed to identify nerve fibers innervating the urethral sphincter and to provide a three-dimensional representation of their tissue relations in the female human fetus. MATERIALS AND METHODS: Histology and immunohistochemistry (Masson's Trichromic, Luxol Fast Blue, Protein S 100 immunostaining and smooth fiber actin immunostaining) were performed on the external urethral sphincter of ten female fetuses with a crown-rump length of 112 to 340mm. Three-dimensional reconstructions of the urethral structure and innervation were obtained from serial sections using Surf Driver 3.5.3 software (David Moody and Scott Lozanoff). RESULTS: Three-dimensional reconstructions of the same sections with different stains demonstrated the precise structure of the muscle layers (smooth and striated muscle fibers) and nerve fibers (myelinated and unmyelinated) and their relations with the urethra and vaginal wall. The proximal third consisted of a circular smooth muscle sphincter, the middle third consisted of two circular layers of smooth and striated muscle fibers and the distal third consisted of a circular layer of smooth muscle fibers surrounded by an omega-shaped layer of striated muscle fibers. In the proximal third of the urethral sphincter, myelinated fibers were identified running with unmyelinated fibers from the pelvic plexus. These fibers were closely related to the lateral and anterior aspects of the vagina. Unmyelinated fibers entered the smooth muscle part of the sphincter at 4 o'clock and at 8 o'clock. Most myelinated fibers entered the sphincter at 3 o'clock and at 9 o'clock. CONCLUSION: Histological and immunohistochemical three-dimensional reconstruction of the anatomical structures of the urethral sphincter provides a better understanding of the origin and nature of the Innervation participating in urinary continence. It provides a very informative view of the three-dimensional arrangement of sphincter muscle layers.     

Histochemical study of human external urethral sphincter]

Human external urethral sphincters (n = 13) were studied histochemically, using ATP-ase staining. The proportions of constituent muscle fiber types (slow twitch type 1 fibers: 35.6-97.7%, mean 65.7%, SD 16.6) were different among the individuals. There were no significant relationships between the percentage of type 1 fibers and the sex or the age. As for the mean muscle fiber diameter of 13 cases, the sizes of type 2 fibers (19.2-42.4 um, mean 27.8 um) were significantly (p less than 0.05, t-test) larger than those of type 1 fibers (15.7-30.3 um, mean 22.3 um). In analyses of individual cases, 10 male cases had significantly larger type 2 fibers than type 1. Two of 3 female cases had no significant difference in diameter between the two fiber types and the remaining 1 female case, in contrast with male cases, had significantly larger type 1 fibers than type 2. There was no significant relationship between the proportions and the diameters of constituent muscle fiber types. Our study thus showed extreme interindividual variation and implicated the presence of sexual difference in human external urethral sphincter muscle.     

Histochemical and contractile properties of striated muscles of urethra and levator ani of dogs and sheep

AIMS: To understand their possible importance in long- and short-term control of continence, some properties of the striated muscles of the urethra and pelvic floor (levator ani) of dogs and sheep were investigated, especially fiber types and contractile characteristics. MATERIALS AND METHODS: Striated muscles of urethra and levator ani of 29 male and 6 female dogs and 11 male and 6 female sheep were removed and cut into strips. Some strips were frozen and stained for ATPase at pH 9.4 and 4.3 for fiber typing; others were set up in an organ bath to study contractile responses to nerve stimulation. RESULTS: All muscles contained both type I (slow) and type II fibers, ranging from 97% type II in female greyhound urethra to 60% in female sheep levator ani. For each muscle, there were fewer type II muscles in sheep than in dog. The diameters of the urethral fibers were about 60% of the levator ani in dogs and 34% in sheep. Contraction of the urethral muscle was faster than for levator ani and declined to about 80% of the peak, 500 msec after the beginning of stimulation at 20 Hz. The levator ani contraction rose to a steady level as long as stimulation continued. CONCLUSIONS: Both the levator ani and urethral striated muscles contain slow and fast fiber types. The levator ani muscles are capable of sustained contraction with rapid onset which will produce long-term closure of the urethra. The circular urethral muscle contraction was faster but less well maintained.     

Histochemical study of external urethral sphincter in the rabbit. Analysis with construction of histograms

Male rabbit's external urethral sphincter was examined by histochemical muscle fiber typing (myosin ATP-ase staining), and the analysis with construction of histograms regarding to muscle fiber types were performed. Rabbit's external urethral sphincter was predominantly composed of fast twitch (type 2) fibers (87.3%) as a whole. But the proportion of constituent fiber types varied according to the layers, i.e., the slow twitch (type 1) fibers constituted a relatively high percentage (33.4%) in the inner third layer, while few of the type 1 fibers were found in the outer third layer. The all histograms regarding to fiber type in different layers were normal bell-shaped distribution curves. The mena diameter of type 2 fibers (14.7 microns) was evidently larger than that of type 1 fibers (20.5 microns). All three kinds of muscle fibers equally tended to increase in size toward the outer direction, and in every three layers, the diameter of type 2 was larger than that of type 1 also. The definite differences in the proportion of fiber types and fiber sizes between layers may implicate that the inner and outer layers play different roles, i.e., continuous tonic constriction in the former and sporadic strong constriction of short duration in the latter, under different neural regulations. As far as rabbit's external urethral sphincter is concerned, sporadic strong constriction should be mainly dependent on the muscle fibers of large size composing the outer layer, especially the fast twitch fibers. It is possible that the rabbit is so adapted that it could interrupt urination promptly.     

Urethral striated muscle and extracellular matrix morphological characteristics among mildly diabetic pregnant rats: translational approach

Introduction and hypothesis

Diabetes mellitus (DM) during pregnancy is associated with high levels of urinary incontinence (UI) and pelvic floor muscle dysfunction. Mild DM can lead to changes in urethral striated muscle and extracellular matrix (ECM) in pregnant rats considering both structures as an entire system responsible for urinary continence.

Methods

Ninety-two female Wistar rats were distributed in four experimental groups: virgin, pregnant, diabetic, and diabetic pregnant. In adult life, parental nondiabetic female rats were mated with nondiabetic male rats to obtain newborns. At the first day of birth, newborns received citrate buffer (nondiabetic group) or streptozotocin 100 mg/kg body weight, subcutaneous route (mild DM group). At day 21 of the pregnancy, the rats were lethally anesthetized and the urethra and vagina were extracted as a unit. Urethral and vaginal sections were cut and analyzed by: (a) cytochemical staining for ECM and muscle structural components, (b) immunohistochemistry to identify fast- and slow-muscle fibers, and (c) transmission electron microscopy for ultrastructural analysis of urethral striated muscle.

Results

In comparison with the three control groups, variations in the urethral striated muscle and ECM from diabetic pregnant rats were observed including thinning, atrophy, fibrosis, increased area of blood vessels, mitochondria accumulation, increased lipid droplets, glycogen granules associated with colocalization of fast and slow fibers, and a steady decrease in the proportion of fast to slow fibers.

Conclusions

Mild DM and pregnancy can lead to a time-dependent disorder and tissue remodeling in which the urethral striated muscle and ECM has a fundamental function.     

Nitroxergic innervation of the human ureterovesical junction

Nitric oxide synthase (NOS) immunohistochemistry and nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry were used to investigate the distribution of nitroxergic, i.e., nitric oxide-synthesizing, neuronal perikarya and processes in the human ureterovesical junction (UVJ). Tissue specimens obtained from two cadaver kidney donors and two patients undergoing radical cystectomy for bladder cancer were examined. Clusters of NOS-immunoreactive neurons were localized in extramural ureterovesical ganglia. NOS-containing nerve fibers traveled within large extramural nerve trunks and marched among smooth muscle bundles. Extramural and intramural blood vessels were encircled by varicose NOS-positive axonal processes. The distribution of NOS immunoreactivity paralleled the staining pattern for NADPH-d activity. Urothelium stained strongly for NADPH-d activity but showed no NOS immunolabeling. Specimens from all four patients investigated showed similar staining patterns. Our results suggest that nitric oxide, a potent smooth-muscle-relaxing neurotransmitter in the autonomic nervous system, plays a physiologic role in opening the human UVJ.     

Adrenergic innervation of the striated muscle of the intrinsic external urethral sphincter from patients with lower motor spinal cord lesion

The adrenergic innervation of smooth and striated muscle components of the intrinsic external urethral sphincter from patients with suprasacral lesions and detrusor-sphincter dyssynergia has been described previously, when no adrenergic nerves were found associated with striated muscle fibers. In our study the intrinsic external urethral sphincter from patients with lower motor neuron lesions and detrusor areflexia was studied histochemically using the glyoxylic acid method to visualize catecholamines. Varicose adrenergic nerves were demonstrated in the smooth muscle. Adrenergic nerve fibers also were found along the edge of individual striated muscle fibers as well as around striated muscle bundles. Blood vessels in both regions of the urethral sphincter were innervated by adrenergic nerves. We conclude that in patients with lower motor neuron lesions and detrusor areflexia there is a substantial invasion by adrenergic nerve fibers in relation to smooth and striated muscle in the urethra, although the function of the nerve fibers is not known.     

Pudendal nerve stimulation of a preparation of isolated guinea-pig urethra

OBJECTIVE: To assess the functional response of the urethral striated muscle to activation of its nerves, using a novel isolated organ-bath preparation. MATERIALS AND METHODS: The urethra of the female guinea-pig was chosen as a suitable model for investigation, as it is functionally and structurally similar to the human urethra. Female Dunkin-Hartley guinea-pigs (400-500 g) were used; for the histochemical and immunohistochemical experiments, unfixed urethras were cryo-sectioned (14 microm thick) and were stained using established methods. For in vitro experiments, whole urethras were suspended vertically, with pudendal nerves intact, for isometric tension and intraluminal pressure recording in a 40-mL organ bath. Drugs were applied directly to the bathing solution. RESULTS: In the striated muscle layer of the urethra there was positive beta-NADPH-diaphorase activity. In organ-bath studies the pudendal nerve-evoked contractions (0.2 ms pulses, 5 s trains, 70 V and 1-100 Hz) were abolished in the presence of tubocurarine (10(-6)m), and unaffected by guanethidine and atropine (both 10(-6)m). Pre-incubation with sodium nitroprusside and SIN-1 chloride significantly reduced the initial peak pressure responses (P < 0.05, anova for paired data) evoked by electrical field stimulation of the pudendal nerves at stimulus parameters of 0.2 ms pulses, 5 s trains, 70 V and 25 Hz. CONCLUSION: Electrically induced contractions were abolished by tubocurarine, confirming that the pudendal nerve innervates the striated muscle of the guinea-pig external urethral sphincter via nicotinic receptors. beta-NADPH-diaphorase histochemistry gave positive staining around guinea-pig striated muscle cells and possibly identified neuromuscular junction sites staining positively for the nitric oxide synthase marker. Together with the results of the organ-bath experiments, the results suggest that the striated muscle cells of the guinea-pig urethra have the machinery to respond to nitric oxide.     

CO-LOCALIZATION OF CARBON MONOXIDE AND NITRIC OXIDE SYNTHESIZING ENZYMES IN THE HUMAN URETHRAL SPHINCTER

PURPOSE: Ineffective relaxation of the urethral sphincter during micturition can result in obstructive voiding symptoms. Several studies suggest carbon monoxide (CO) acts alongside nitric oxide (NO) as an inhibitory neurotransmitter, and may regulate NO production. We have investigated the distribution of the constitutive CO producing enzyme, heme oxygenase-2 (HO-2) and the NO producing enzyme, neuronal nitric oxide synthase (nNOS), in the human urethra. MATERIALS AND METHODS: Transverse cryostat sections (12 microns.) were cut from three male membranous and six female urethrae. Double immunofluorescence was carried out for co-localization of HO-2 with nNOS using standard methodology. RESULTS: Nerve trunks showing both HO-2 and nNOS immunoreactivities were identified in the urethrae in both sexes. In the female urethrae, of 152 ganglionic cell bodies expressing HO-2 or nNOS immunoreactivity, 74.3% exhibited both HO-2 and nNOS immunoreactivities, 25% exhibited only HO-2 immunoreactivity and 0.7% exhibited only nNOS immunoreactivity. CONCLUSIONS: Immunoreactivity for HO-2 has been demonstrated in neuronal structures innervating the male and female urethral sphincters. The dual expression of HO-2 with nNOS immunoreactivity in cell bodies and nerves suggests that there is an interaction between the CO and NO generating systems. Abnormality in these systems may play a role in urethral dysfunction.     

Effect of vardenafil on nitric oxide synthase expression in the paraventricular nucleus of rats without sexual stimulation

Vardenafil hydrochloride (HCl) is a potent and selective phosphodiesterase type-5 (PDE-5) inhibitor that enhances nitric oxide (NO)-mediated relaxation of human corpus cavernosum and NO-induced rabbit penile erection, and enhances erectile function in patients. In the present study, the effect of vardenafil on nitric oxide synthase (NOS) and neuronal NOS expressions in the paraventricular nucleus (PVN) of rats without sexual stimulation was investigated using nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry and neuronal NOS (nNOS) immunohistochemistry and western blot analysis. The present results showed that NOS and nNOS expression in the PVN was increased by vardenafil treatment as the dose- and duration-dependently without sexual stimulation. The phosphodiesterase type-5 inhibitor, vardenafil, augmented NOS expression in the brain without sexual stimulation. The present study suggests that sexual behaviour can be directly modulated by neurotransmitters such as nitric oxide.     

Functional conditions of micturition induced by selective sacral anterior root stimulation: experimental results in a canine animal model

Electrical stimulation of the sacral anterior roots using conventional rectangular current pulses results in a simultaneous contraction of the urinary bladder and the striated urethral sphincter. Using a tripolar nerve cuff electrode with quasitrapezoidal current pulses and appropriate stimulation parameters, hyperpolarization of the nerve-fiber cell membrane under the anode of the stimulating electrode can reversibly arrest action potential propagation in large myelinated nerve fibers, innervating the striated urethral sphincter, while leaving action potential propagation unaffected in small non-myelinated nerve fibers innervating the urinary bladder smooth muscle (anodal arrest). Using this technique in 19 female mongrel dogs, we studied the effect of bladder filling, level of anesthesia, and sacral deafferentation on bladder pressure, urethral pressure, and urinary flow. Effective micturition could be induced only after complete dorsal rhizotomy, abolishing reflex contraction of the striated urethral sphincter, when blocking quasitrapezoidal current pulses were used for stimulation. Stimulation with rectangular current pulses directly induced a rise in distal urethral pressure, preventing micturition during stimulation.     

Urethral pressure variations in women with neurourological symptoms: II. Relationship to urethral smooth muscle

Simultaneous urethrocystometry and electromyography from the urethral striated muscle during bladder filling was performed on female patients complaining of neurourological symptoms. Their maximum urethral pressure varied between 20 and 84 cm H₂O. To study the effect of the urethral smooth muscle on the urethral pressure variations, a bilateral pudendal block was applied successfully in 12 patients. It was found that in 1 patient the urethral pressure variations were caused by the urethral striated muscle only, in 4 patients they were caused mainly by the urethral striated muscle, in 2 other patients they were caused equally by urethral striated and smooth muscle, and finally in 5 patients mainly by urethral smooth muscle. By eliminating the urethral striated muscle activity by pudendal block the maximum urethral pressure was reduced 20 to 84%.     

Neuroanatomy of the human female lower urogenital tract

PURPOSE: The neuroanatomy of the female lower urogenital tract remains controversial. We defined the topographical anatomy and differential immunohistochemical characteristics of the dorsal nerve of the clitoris, the cavernous nerve and the nerves innervating the female urethral sphincter complex. MATERIALS AND METHODS: A total of 16 normal female human pelvic specimens at 14 to 34 weeks of gestation were studied by immunohistochemical techniques. Serial sections were stained with antibodies raised against the neuronal markers S-100 and neuronal nitric oxide synthase (nNOS), vesicular acetylcholine transporter, calcitonin gene-related peptide and substance P. The serial sections were computer reconstructed into 3-dimensional images. RESULTS: Under the pubic arch at the hilum of the clitoral bodies the branches of the cavernous nerves joined the clitoral dorsal nerve to transform its immunoreactivity to nNOS positive. The cavernous nerves originated from the vaginal nervous plexus occupying the 2 and 10 o'clock positions on the anterolateral vagina and they traveled at the 5 and 7 o'clock positions along the urethra. The urethral sphincter complex was innervated by nNOS immunoreactive and nonimmunoreactive nerve fibers arising from the vaginal nervous plexus and pudendal nerve, respectively. CONCLUSIONS: The dorsal nerve of the clitoris receives nNOS positive branches from the cavernous nerve as a possible redundant mechanism for clitoral erectile function. The urethral sphincter complex has dual innervation, which pierces into the urethral sphincter complex at different locations. The study of the neuroanatomy of the female lower urogenital tract is germane to the strategic design of female reconstructive surgery.     

雌性大鼠尿道横纹括约肌的显微解剖研究

目的:研究雌性大鼠尿道横纹括约肌的显微解剖,以深入了解控尿机制的主要部位.方法:取3月龄雌性Wistar大鼠4只,用水合氯醛腹腔注射麻醉后,解剖膀胱和尿道全长标本,在福尔马林中固定,石蜡包埋,2只做平行尿道长轴的纵行切片,2只做垂直尿道的横行切片,组织切片做常规HE染色、Masson三色染色、Mallory磷钨酸苏木精染色,以观察尿道的显微解剖,重点了解尿道横纹括约肌.结果:雌性Wistar大鼠的尿道为一长1.5～2.0 cm的管状结构.其典型的组织结构由外向内依次为环形横纹肌纤维层、环形平滑肌纤维层、纵行平滑肌纤维层、致密结缔组织层和上皮层.全尿道标本纵切面显示尿道壁内横纹括约肌并不分布于尿道全长,而是仅环绕尿道的中下段.横切面显示尿道壁内横纹括约肌呈封闭环形,约5～10层不等,但并不是均匀分布,后壁横纹肌层较前壁为厚,层数稍多.结论:尿道横纹括约肌呈封闭环形分布于雌性大鼠尿道的中外段,提示此处为控尿机制的主要部位.     

The fiber type of the rabbits' striated external urethral sphincter: electrophoretic analysis of myosin

The fiber type of the rabbits' external urethral sphincter was investigated with O'Farrell's 2-dimensional electrophoresis of constituent proteins of glycerinated muscle, peptide mapping of myosin heavy chains and non-denaturing pyrophosphate gel electrophoresis of myosin. It was determined as fast type by all three methods. The relative proportions of muscle fibers which were estimated from myosin light chain contents were 88 per cent fast type and 12 per cent slow type. On the basis of the results presented, it was shown to be fast twitch muscle, but not identical to the psoas muscle.     

Diagnostic value of histochemistry in embryonal rhabdomyosarcoma.

Embryonal rhabdomyosarcomas from the nasopharynx of two children were examined by histochemical methods commonly applied to muscle biopsies. These stains included nicotinamide adenine dinucleotide-tetrazolium reductase (NADH-TR), succinate dehydrogenase (SDH), PAS, PAS-diastase, myophosphorylase, calcium-mediated adenosine triphosphatase (ATPase) preincubated at high and low pH, and oil red O. Myofibrils were easily identified with ATPase and blood vessel walls were also stained. NADH-TR clearly showed longitudinal and cross-striations that were not seen with H&E or PTAH stains. The modified Gomori trichrome stain additionally contributed to the recognition of myofibrils. Some techniques of muscle histochemistry applied to fresh frozen sections of tumor tissue may provide evidence of muscular differentiation in otherwise poorly differentiated sarcomas for a more accurate diagnosis of rhabdomyosarcoma.     

Halothane minimum alveolar anesthetic concentration and neuronal nitric oxide synthase activity of the dorsal horn and the locus ceruleus in rats.

There is some evidence of a relationship between nitric oxide and pain control pathways. However, it is still controversial whether nitric oxide synthase (NOS) inhibitors affect minimum alveolar anesthetic concentration (MAC). We examined the effects of 7-nitro indazole (7-NI), a selective neuronal NOS (nNOS) inhibitor, on halothane MAC. With nicotinamide adenine dinucleotide phosphate diaphorase histochemistry, we also investigated the nNOS activity of the dorsal horn and the locus ceruleus in 26 Sprague-Dawley rats. 7-NI (100, 500, 1000 mg/kg intraperitoneally) reduced halothane MAC to 0.34% +/- 0.12%, 0.1% +/- 0.03%, and 0.05% +/- 0.12%, dose dependently (P < 0.01). 7-NI also reduced the number of nicotinamide adenine dinucleotide phosphate diaphorase-positive cells by 20% to 65% (P < 0.05 or 0.01) and the staining intensity of the axons in the locus ceruleus and lumbar and thoracic spinal cord as compared with the control group. 7-NI reduced the MAC observed with halothane anesthesia, which was accompanied by nNOS activity suppression in the spinal cord and the locus ceruleus. Our results support the hypothesis that the nitric oxide signaling pathway is related to MAC. IMPLICATIONS: We examined the effects of a selective neuronal nitric oxide synthase inhibitor, 7-nitro indazole, on halothane minimum alveolar anesthetic concentration and measured the nitric oxide synthase activity in the spinal cord and the locus ceruleus of Sprague-Dawley rats using nicotinamide adenine dinucleotide phosphate diaphorase staining method. 7-Nitro indazole decreased both the minimum alveolar anesthetic concentration and neuronal nitric oxide synthase activity.     

Electrophoretic and ultrastructural analysis of the rabbit's striated external urethral sphincter

The male rabbit's external urethral sphincter was investigated with O'Farrell's 2-dimensional electrophoretic analysis of myosin light chains and electron microscopy. Its pattern of myosin light chains was different from that of the soleus (predominantly slow twitch muscle) but was very similar to that of the psoas (predominantly fast twitch muscle). Ultrastructurally it was shown to be red muscle resembling the soleus. Therefore the fiber type of the rabbit's external urethral sphincter was determined to be the red (fast) type.