Tyrosine hydroxylase- and nitric oxide synthase-immunoreactive nerve fibers in mitral valve of young adult and aged Fischer 344 rats

Using confocal fluorescence microscopy we studied, in whole mounts of heart mitral valves of young adult and aged Fischer 344 rats, the distribution of nerves containing the catecholamine marker tyrosine hydroxylase (TH) or the synthetic enzyme marker for nitric oxide, nitric oxide synthase (NOS). TH-IR was localized in two separate nerve plexuses which do not intermingle. The 'major' plexus arose from the annulus region, traversed the basal zone of the valve, and ramified in the intermediate zone to form a dense network of fine fibers. The 'minor' plexus was restricted to the distal zone and originated from bundles that ascended the chordae tendineae to enter the valve cusp. A concentric zone located between the major and minor plexuses was devoid of TH-IR nerve fibers. Both plexuses demonstrated (i) nerves that contained numerous varicosities along the length of each fiber, (ii) many terminal axons and (iii) different shaped terminal axon endings. With age, the density of TH-IR innervation in the mitral valve was markedly reduced; and nerve fibers of the minor plexus were limited to the chordae tendinae, without extending into the valve cusp itself. NOS-IR fibers in the mitral valve formed a loose network that extended from the annulus to more than halfway down the cusp. The varicose beads of the terminal NOS-IR axons appeared to become progressively smaller and less intensely fluorescent until they disappeared at the terminal endings, which showed no specializations. No NOS-IR fibers were observed in the distal zone of the valve leaflet or in the chordae. In the aged mitral valve, the density of NOS-IR nerves was decreased, as compared with NOS-IR innervation in the young adult valve. The existence of TH and NOS as well as other signal molecule markers in heart valve nerves and the disparate patterns of their distribution and localization provide evidence supporting the theory that heart valve nerves form a complex reflexogenic control system in the mitral heart valve. In summary, two distinct neural architectures are described for TH-IR and NOS-IR valve nerves, respectively. The former are believed to be axons dedicated to sympathetic motor functions. The NOS-IR valve nerves may have sensory and/or postganglionic parasympathetic motor functions. An implication of these findings is that different, but perhaps related, valve functions may be mediated by separate, dedicated circuits.     

Myelinated nerve fibre analysis of the human small splanchnic nerve

The aim of the present study is to analyse nerve fibres of the human small splanchnic nerve in relation to the ageing process. The analysis was conducted with the use of a new staining method that makes it possible to discriminate various structures of the nervous tissue. An image-analysing digitiser, a microscope with a drawing tube and a personal computer for storing data and performing statistical analyses were employed in this study. We examined 30 human small splanchnic nerves which were taken from cadaver specimens (20 males and 10 females) aged from 44 to 96 years. Our report may provide a first information concerning the ageing process of the human small splanchnic nerve. The results indicate that a decrease in transverse area and perimeter of myelinated axons in one of the important changes occurring in the human small splanchnic nerve with the ageing process.     

Evaluation and treatment of posterior cruciate ligament injuries

Twenty-eight low median nerve injuries and 23 low ulnar nerve injuries were repaired using intraneural fascicular dissection and electrical fascicular orientation. Eleven freshly lacerated nerves were seen within 48 hours after injury; 40 nerve lacerations were chronic. Fascicular orientation between sensory and motor fascicles at the proximal nerve end could be accurately differentiated in 47 nerves (92%) independent of whether it was acute or chronic. At the distal nerve end in fresh lacerations, the motor fascicles could be determined conclusively by muscle contraction with sequential electrical stimulation of the fascicles. In chronic nerve lacerations, the distal fascicles could be estimated anatomically after internal neurolysis. After fascicular orientation, nerves were repaired with end-to-end group fascicular suture or interfascicular sural nerve grafting. Twenty-four nerves repaired with end-to-end suture and 13 nerves repaired with nerve grafting were monitored more than 25 months. Satisfactory sensory results (i.e., S3+ or S4 functions) were obtained in 29 nerves (78%) and M4 or M5 motor functions were achieved in 29 nerves (78%). There were no patients who needed additional tendon transfers to reconstruct thumb opposition or to correct claw finger deformity. These results suggest that low median or ulnar nerve lacerations, whether acute or chronic, partial or complete, may be successfully repaired with the aid of electrical fascicular orientation with or without intraneural fascicular dissection.     

Protective coating of cranial nerves with fibrin glue (Tissucol) during cranial base surgery: technical note

OBJECTIVE: Cranial nerve deficit, either transient or permanent, is a common postoperative complication after cranial base surgery. Frequently, this occurs because intracranial nerves are directly involved in the cranial base lesion. However, any cranial nerve adjacent to the lesion can be damaged because of direct or indirect manipulation during surgery, leading to severe morbidity. We describe a new technique in which the adjacent intracranial nerves are protected from surgical trauma by coating the nerves with a biological two-component fibrin glue (Tissucol; Immuno A.G., Vienna, Austria). SURGICAL TECHNIQUE: The technique was performed in patients who underwent cranial base surgery for different types of lesions. After exposure of the operating field, the cranial nerves that were at risk of operative trauma were coated with a thin layer of fibrin glue using a double lumen catheter within a traditional suction device. RESULTS: With the application of fibrin glue, a protective layer of a rubbery consistency is formed around the nerve. No intraoperative complications or adverse effects of the application were noted. Moreover, no surgical injury of the nerves occurred and no or minimal postoperative cranial nerve deficit was noted in the coated nerves. CONCLUSION: Although it is difficult to compare the postoperative cranial nerve deficit in the coated nerves with a control group, we think that this technique is a valuable method to minimize or avoid intraoperative cranial nerve injury during cranial base surgery.     

A quantitative study of nerve fibers in the human facial nerve

The facial and intermediate nerves were quantitatively evaluated in seven patients who died from systemic malignancies not involving the facial nerve. In addition, five of the specimens were also qualitatively evaluated by measuring the total and axon diameters of the facial and intermediate nerve fibers. In two cases the facial nerve fibers were counted at five different levels. The total number of myelinated nerve fibers in the facial nerve varied from 7500 to 9370. The total number of myelinated nerve fibers in the intermediate nerve varied between 3120 and 5360. The peak diameter of the facial nerve axon was between 4 and 6 microns, and was between 2 and 3 microns in the intermediate nerve. When comparing nerve segments at different anatomical levels, the largest amount of nerve fibers was found at the level of the middle mastoid portion. However, this number did not reach the amount of nerve fibers counted in the internal acoustic meatus.     

Age-related changes in sympathetic modulation of sensory nerve activity in rat skin

OBJECTIVES: Sensory nerves play an important role in mediating neurogenic inflammation and subsequent tissue healing. A decrease in sensory nerve function with increasing age has been reported to correlate with poor tissue healing. Sympathetic nerves are known to modulate sensory nerve function, and changes in this modulation could also have important implications with ageing. The aims of this study were to examine the effect of different frequency electrical stimulation (ES) on the microvascular responses obtained to sensory nerve activation in young, aged and capsaicin-pretreated rats and modulation of these responses by sympathetic efferents. METHODS: Using laser Doppler flowmetry, vascular responses to antidromic ES of the sciatic nerve were monitored in the base of vacuum-induced blisters in the hind footpad. The non-selective alpha-adrenoceptor antagonist phentolamine (3 mg/kg, i.v.) was administered 20 min prior to ES. RESULTS: At high frequency ES (20V, 2ms, 15Hz for 1 min), the vascular response in old rats was significantly reduced (46 percent decrease, p < 0.05) compared to young control. At low frequency ES (20 V, 2 ms, 5 Hz for 1 min) however, older rats produced similar vascular responses to the young. Capsaicin-pretreated rats showed significantly reduced vascular responses to both high and low frequency ES, regardless of age. Pretreatment with phentolamine significantly increased the microvascular response in young rats at high (87 percent) and low (36 percent) frequency ES. In contrast, phentolamine significantly increased the ES-induced response in old rats at high frequency only (147 percent increase). CONCLUSIONS: The results suggest that the aged sensory nerve responds preferentially to low frequency ES and that sympathetic efferents exert an inhibitory modulatory effect on the vascular response evoked by sensory nerve stimulation. There are age-related changes in sympathetic modulation of sensory nerve-mediated responses which is dependent on stimulation frequency.     

Separation of chiral polychlorinated biphenyls by micellar electrokinetic chromatography using beta- and gamma-cyclodextrin mixtures in the separation buffer

The present study was designed to compare regenerative potential of normal and degenerated nerve grafts. Peripheral nerves in rats were induced to undergo in situ degeneration for a period of 6 weeks, 3, 6 and 12 months. During early phase of denervation the myelin and axons degenerated and were absorbed. With prolonged denervation (i.e. 12 months), such nerves were reduced in size and exhibited extensive fibrosis. A 2 cm long segment of the degenerated nerve was transplanted in an surgically created gap in the host peroneal nerve to evaluate their regeneration supporting ability. Regeneration of host axons occurred rapidly through nerves degenerated for a period up to 3 months. The extent of regeneration was compromised in 6-month degenerated nerve group, and was significantly reduced in the 12-month degenerated nerve grafts. These results show that with extended degeneration interval, the regeneration supporting ability of nerves is compromised. It is concluded that nerve repair should not be excessively delayed in order to compromise recovery.     

A quantitative assessment of innervation in the conduction system of the calf heart

BACKGROUND: The aim of the present investigation was to determine the relative distribution of autonomic and sensory nerves in the cardiac conduction tissues of calves. METHODS: A quantitative immunohistochemical and histochemical technique was adopted. RESULTS: Immunoreactivity to the general neuronal marker protein gene product 9.5 (PGP 9.5) demonstrated that all regions of the conduction system possessed a higher relative density of total nerves when compared with the surrounding myocardial tissues. Unlike myocardial innervation, the conduction system did not display an atrial-to-ventricular gradient in nerve density. PGP 9.5-immunoreactive nerve trunks and varicose nerve fibres were more numerous in the transitional atrioventricular node and the penetrating atrioventricular bundle than in either the sinus node, compact atrioventricular node, or bundle branches. The Purkinje network of the ventricular conduction tissues possessed a rich supply of PGP 9.5-immunoreactive nerve trunks and varicose nerve fibres. Acetylcholinesterase (AChE)-positive nerves were the main subtype identified in the sinus and atrioventricular nodes and in the ventricular conduction tissues, representing 50-80% of the area occupied by PGP 9.5-immunoreactive nerves. The compact atrioventricular node possessed AChE-positive and tyrosine hydroxylase (TH)-immunoreactive nerves in similar proportions (45%), although, in general, TH-immunoreactive nerves had a lower relative nerve density than AChE-positive nerves. Neuropeptide Y (NPY)-immunoreactive nerves represented the main peptide-containing subpopulation and occurred throughout the conduction system, displaying a similar pattern of distribution and relative density to those demonstrating TH immunoreactivity. Nerve fibres immunoreactive for somatostatin, vasoactive intestinal polypeptide, substance P, and calcitonin gene-related peptide formed relatively minor subpopulations. CONCLUSIONS: The general innervation of the bovine conduction tissues exhibits significant regional variation. Throughout all regions of the conduction system, AChE-positive nerve represented the dominant subtype when compared with TH- and NPY-immunoreactive nerves. The distribution and relative density of nerve subtypes in the tissues of the bovine conduction system are similar to those observed in man, whereas differences were observed in other regions, such as the atrioventricular bundle and bundle branches. This finding must be considered by those making interspecies comparisons.     

Re-intervention in the anal region

In 29 rats, responses evoked by pelvic and hypogastric nerve stimulation were recorded from postganglionic nerves to bladder and penis (clitoris). Responses to pelvic nerve stimulation had nonsynapsing and synapsing components. The nonsynapsing component was relatively large in main nerve to penis and small in lateral nerve to penis and nerves to bladder. Pelvic nerve fiber synapsing on pelvic ganglion neurons to bladder had a large subliminal fringe, while fibers synapsing on neurons supplying penis (clitoris) had a small subliminal fringe. Recruitment was greater in nerves to bladder and lateral nerve to penis (clitoris) compared to main nerve to penis (clitoris), indicating more synapsing fibers in the former nerves. Almost all hypogastric fibers to bladder were direct. A small subliminal fringe was demonstrated for hypogastric fibers synapsing on neurons supplying penis. No subliminal fringe was evident for the bladder. Pelvic and hypogastric nerve interaction on pelvic ganglion neurons could not be demonstrated with either single shock or tetanic trains of conditioning stimuli. With antidromic stimulation, conduction velocities of afferent fibers in pelvic nerve ranged from 0.15 m per sec to 2.9 m per sec. In hypogastric nerve they ranged from 0.35 m per sec to 2.8 m per sec.     

The canine urinary bladder and prostate

Nonrecurrence and variations in the ascending course of the recurrent laryngeal nerves make it essential to identify the nerve to avoid injury to it during thyroidectomy. We believe that visual identification of the nerve without undue handling is all that is necessary. The recurrent nerve is no more delicate than other similar nerves. Unilateral injury to the recurrent nerve may result in temporary hoarseness which will improve with time. Some restriction of the airway during exertion may be present. Bilateral injury to the recurrent nerves may produce initially a loss of voice without airway constriction. Later the voice may return, accompanied by serious respiratory embarrassment on exertion.     

Defective gas mixers, a cause of retro-pollution of medical gas distribution pipelines]

PURPOSE: To study the distribution and mechanism of traumatic injuries to the nerves supplying the eye and muscles protecting the visual apparatus. METHODS: Brain autopsy was carried out in 12 consecutive patients who died within three days after closed head injury. A segment of the brainstem with the entire intracranial portion of nerves II-VII was dissected out in each case and fixed in formalin. The specimens were stripped of the leptomeninges and inspected thoroughly under magnification. RESULTS: Injuries to the nerves were seen in nine subjects. The oculomotor nerve was completely torn off from the midbrain unilaterally in three and bilaterally in two cases. In one patient only a portion of the superficial fibres on the medial aspect of the nerve was ripped out from the brainstem. In two patients the fourth nerve was ruptured. The root of the fifth cranial nerve was contused and the fibres between the brainstem and Gasserian ganglion crushed and separated in one case. Bilateral avulsion of the root of the sixth nerve from the brainstem was found in two cases. The initial segment of the facial nerve was crushed in two subjects. No visible injury to the optic nerves was found. CONCLUSIONS: Cranial nerves related to the visual system are subject to serious injury in a large proportion of cases of severe head trauma resulting from automobile accidents. In the majority of cases damage results from ripping the roots of these nerves out of the brainstem.     

The trochlear nerve: anatomy by microdissection

This work is based on the microscopic study of 30 trochlear nerve trunks (15 heads). In 17 cases, the trunk arose from two nerve bundles, in 8 cases from one bundle, and for the other 5 nerves, three or four bundles. The mean total length of the trochlear nerve was 86 mm. The nerve may be separated into the 3 following parts: infratentorial, intracavernous, intraorbital. In all 30 cases studied, the first part of the nerve was infratentorial, thus leading us to suggest the term "infratentorial part" for this segment of the nerve. In 27 cases, contact was found with the superior cerebellar artery, in the infratentorial part. In the intracavernous part of ten nerves we found two rami tentorii and in eight cases fibers were exchanged with the ophthalmic nerve. In the orbit, 18 trochlear nerves crossed the posterior ethmoidal artery. 23 trochlear nerves ended on the medial face of the superior oblique muscle. The remaining 7 ended at the superior border of the muscle.     

Variations in uterine innervation during the estrous cycle in rat

Uterine innervation undergoes profound remodeling during puberty, pregnancy, and after parturition. However, the extent to which uterine innervation may change during the estrous cycle is uncertain. The objective of the present study was to determine whether nerve fiber density of the uterine horn is altered during the estrous cycle and, if so, which subpopulations are affected. Immunostaining for the pan-neuronal marker protein gene product (PGP) 9.5 revealed fibers within the vascular zone, myometrium, and endometrium, with greater density in the ovarian and cervical regions than in the middle. In most structures, nerve density was reduced during estrus. This could not be accounted for by increased target volume, as the reduction in longitudinal muscle innervation persisted after correction for changes in target size. Immunostaining for vasoactive intestinal polypeptide-immunoreactive parasympathetic nerves revealed fibers associated predominantly with the vascular zone and circular muscle within the cervical region. No cyclical variation was detected. Calcitonin gene-related peptide-immunoreactive nerves were present within all structures, and density was highest at the ovarian end. These fibers also did not vary significantly through estrous. Dopamine beta-hydroxylase-immunoreactive sympathetic nerves innervated all structures, with greater density in the ovarian end. These fibers were reduced substantially during estrus, but the decline was also significant in proestrus, thus preceding that detected by using the pan-neuronal marker. We conclude that the estrous cycle in rat is accompanied by structural remodeling of sympathetic nerves by way of retraction or degeneration of terminal fibers during estrus. The structural loss of the terminal axon apparently is preceded by depletion of catecholamine-synthesizing enzyme.     

Optic neuromyelitis: a necrotizing disease of the central nervous system]

Optic neuromyelitis is characterized by simultaneous or successive necrotizing lesions involving the optic nerves and the spinal cord. We report two females with the disease, aged 30 and 34 years old. In the latter, a neuropathological study was done. Both patients had clinical, neuroradiological and pathological features that differed from those of primary demyelinating syndromes such as multiple sclerosis. These patients illustrate the selectivity of optic nerve and spinal cord lesions. The latter involve mainly pyramidal and Goll tracts while, within the necrotizing lesions of the optic chiasma, the fibers of the unaffected optic nerve are spared. This pattern suggests a selective injury to some population of axons. Blood vessels were not affected in the necrotizing areas and the lesions did not follow a vascular territory, therefore a vascular mechanism causing the disease is unlikely. The clinical and neuropathological features of neuromyelitis optic suggest a selective involvement of some axons.     

Ultrastructural study of peripheral nerve injury induced by monopolar and bipolar diathermy

The effect of unipolar and bipolar electrocoagulation on human and albino rat peripheral nerves was examined by transmission electron microscopy. The greater auricular nerve obtained from operated patients and the femoral nerve of an albino rat were chosen for this study. The nerves were divided into three groups: controls, segments of nerves spot-coagulated with unipolar instruments, and segments of nerves spot-coagulated with bipolar instruments. Significant cell injury, expressed by marked damage of the Schwann cells, was induced by unipolar coagulation in both myelinated and unmyelinated nerves, in humans as well as in the albino rat. However, in bipolar-treated nerves, the Schwann cell architecture remained well preserved in both types of nerves. The results are in favor of bipolar electrocoagulation when applied in areas rich in neurovascular supplies.     

Selective reinnervation of regenerating mixed nerve fibres across a silicone tube gap. Further experimental evidence of neurotropism

This study investigated specific regeneration of a mixed motor and sensory nerve by the method of spinal dorsal root ganglions resection. A 10 mm segment of tibial nerve was resected and the nerve ends inserted in a silicone tube. Fourteen weeks later, dorsal root ganglia from L6 to S1 were resected on the experiment side. Twenty weeks later, the regenerating motor nerve fibres of mixed nerves selectively grew into motor branches. The rate of misdirected growth in mixed nerves was less than 6%. These results suggest that regenerating motor and sensory axons of mixed nerves are able to select their distal target organs accurately. Better results may be obtained using the entubulation repair method.     

Compression and entrapment neuropathies of the lower extremity

Injury to a peripheral nerve from pressure placed on it causes a compression neuropathy. There are particular anatomic sites where individual nerves are most vulnerable. The authors describe the physiology and structural anatomy of peripheral nerves, the pathophysiology of nerve entrapment, and the classification of peripheral nerve injury. Specific compression and entrapment neuropathies of the lower extremity are described in detail.     

Morphology of the male accessory organs of reproduction of immature fallow deer (Dama dama L.) with particular reference to puberty and antler development

Cutting the suspensory ligament reduced the ovarian content of norepinephrine (NE) to less than half that of controls and only a few blood vessels had perivascular fibers and an occasional nerve remained in the interstitial gland. Cutting the ovarian plexus had a less drastic, but similar effect on the ovarian content of NE and on the pattern of ovarian adrenergic nerves. Cutting both the suspensory ligament and ovarian plexus eliminated visualization of ovarian adrenergic nerves, but some ovarian NE was still measurable. Fluorescence and electron microscopic studies of the suspensory ligament revealed a large adrenergic nerve embedded in smooth muscle of the ligament. The nerve was also acetylcholinesterase-positive. Cutting the celiac plexus or incising a small nerve lateral to the plexus and medial to the origin of the suspensory ligament, had the same effect on the ovarian adrenergic nerves as cutting the suspensory ligament. It is concluded that the extrinsic adrenergic nerves to the rat ovary reach the organ by two routes: one via the nerve in the suspensory ligament (superior ovarian nerve), and one via the traditionally described ovarian plexus along the ovarian artery.     

Development of sensory innervation in dentin

We have labeled dental nerves of 3-week- to 1-year-old rats by axonal transport of radioactive protein in order to detect nerves in developing dentin by autoradiography. We found that, in addition to nerve growth, two processes determine adult dentinal nerve location: (1) enclosure of nerves within circumpulpal dentinal tubules during the last few weeks of dentinogenesis, beginning at the tip of the pulp horn and spreading to include most coronal dentin; and (2) gradual loss of the nerves near the tip of the cusp because of dentinal attrition and replacement by noninnervated, reparative dentin. Several days before a molar erupts, nerves at the tip of the cusp have already begun to be enclosed by dentin; 2-3 weeks later, when dentinogenesis at the cusp tip slows down, most of the innervation for that region has been established, nerves extend up to 160 micron into dentin, and the molar has reached the stage of functional occlusion. Soon after initial occlusion, the process of dentinal attrition and replacement by noninnervated reparative dentin begins; however, simultaneous dentinogenesis in more apical regions produces new innervated dentin. We studied nerve position in relation to dentin growth lines and found that there is a long-term association of nerve endings with specific sites in the dentinal tubules. The similarities between the development of dentinal innervation in rat molars and in human permanent teeth are discussed; it is found that as teeth mature and become more sensitive to painful stimuli, the density of dentinal nerves increases.