Comparative anatomy of the thigh nerves of Cebus libidinosus (Rylands et al., 2000)

Non-human primates have constituted an important group among animals subjected to various studies. Ethological, evolutionary and paleontological studies have revealed changes in anatomical structures linked to the evolution of primates, considered in studies on the comparative anatomy between Cebus libidinosus and other neotropical monkeys or those from the Old World, and the detailed knowledge on their anatomy may represent an important factor for their preservation and protection when the animals are brought to veterinary clinics after accidents or illnesses. In terms of veterinary importance, sometimes these animals arrive in the veterinary medical clinics after accidents, needing surgery or clinical treatment, but the little data available on anatomy has impaired the correct proceedings. The main justification for studies on C. libidinosus, is due to little information about the anatomy related to C. libidinosus in Brazilian and worldwide scientific literature. In this study, the distribution, enervation and path of the femoral and sciatic nerves of the pelvic limb (thigh) of C. libidinosus were studied and these results were compared with literature on the anatomy of humans, chimpanzees and baboons. In general, the enervation model of the four primates is identical, but in specific terms, the differences in enervations indicate evolution convergence closer to the branch of baboons in the evolutionary tree, and these data corroborate other comparative studies in relation to the same primates to vessels, muscles and nerves. In conclusion, the nerve organization in the thigh of C. libidinosus is identical to baboon, chimpanzee and homo, but more similar to baboon. The specific differences found indicate an ancient phylogenic origin to C. libidinosus and baboons (data corroborated by other studies).

Retrospective canine skin peripheral nerve sheath tumors data with emphasis on histologic, immunohistochemical and prognostic factors

Abstract: In this retrospective study was determined the frequency of canine skin peripheral nerve sheath tumors (PNST) in cases diagnosed by the Setor de Patologia Veterinária of the Universidade Federal do Rio Grande do Sul (SPV-UFRGS), Brazil, between the years 2000 and 2012. The canine profiles, as well as histological, immunohistochemical and prognostic aspects of the tumors were based on 70 samples, comprising 40 females, 29 males and one unspecified sample. Between 2000 and 2012, 2,984 skin tumors of dogs were diagnosed in the SPV-UFRGS, totaling 2.34% of skin neoplasms in dogs. Animals that comprised the largest amount of samples (43%) were those with no breed (SRD), followed by German Shepherds (10%). Females were more affected than males (40/70 - 57% and 29/70 - 41% respectively). Skin PNST of this research showed predominant localization on the limbs (40% in the forelimbs and 29% in the hindlimbs); affecting adult dogs, mostly aged between 8 and 11 years (54%). The samples were routinely processed for hematoxylin and eosin, and were also evaluated by toluidine blue and Masson's trichrome staining, and immunohistochemistry (IHC) anti-vimentin, -S-100, -GFAP, -actin, von Willebrand factor and neurofilament. Anisocytosis and anisokaryosis, mitotic index, intratumoral necrosis, invasion of adjacent tissues, tumor location, local recurrence and metastasis were related to the diagnosis of benign (49/70) or malignant tumor (21/70). The Antoni A histological pattern was observed more frequently in benign tumors. The immunohistochemistry helped to diagnose PNST, and anti-vimentin and anti-protein S-100 showed the highest rates of immunostaining. Throughout statistical analysis of animals with tumor recurrence, it was found that the chance of an animal with a malignant peripheral nerve sheath tumor to develop recurrence is 4.61 times higher than in an animal that had a benign tumor.

Characterization of nerve-induced relaxation of gastrointestinal sphincteric smooth muscle in a South American opossum (Didelphis albiventris)

The presence of inhibitory nonadrenergic noncholinergic (NANC) intrinsic innervation of the circular muscle of the gastrointestinal sphincters of the South American (SA) opossum was investigated in vitro. Isolated circular muscle strips from the esophagogastric and ileocolonic junctions but not from the gastroduodenal (pylorus) region developed spontaneous tension. Tetrodotoxin (TTX, 1 µM) augmented the spontaneous tension only in the ileocolonic junction strips. Electrical field stimulation of esophagogastric and ileocolonic junction strips caused frequency-dependent responses consisting of a relaxation at lower frequencies (<1 Hz) and a biphasic response or contraction at higher frequencies. In the strips from the pyloric region electrical field stimulation abolished the spontaneous activity at lower frequencies and induced contractions at higher frequencies. The responses elicited by electrical field stimulation in the three sphincters were abolished by TTX (1 µM). Electrical field-induced contractions were reduced while relaxations were enhanced by atropine (1 µM). In the presence of atropine (1 µM) and guanethidine (3 µM), electrical field stimulation, nicotine and ATP induced frequency- or concentration-dependent relaxations of the three sphincters that were abolished by TTX (1 µM). Isoproterenol and sodium nitroprusside caused concentration-dependent relaxations which were TTX-resistant. These findings indicate that the sphincteric circular muscle of the SA opossum gastrointestinal tract is relaxed by the activation of intrinsic NANC nerves and therefore can be used as a model for the study of the mechanisms involved in these responses

Normal median near nerve potential

In routine studies of sensory nerve conduction, only fibers e7 µm in diameter are analyzed. The late components which originate from thinner fibers are not detected. This explains why a normal sensory action potential (SAP) may be recorded in patients with peripheral neuropathies and sensory loss. In the present study we investigated the late component of the median SAP with a near nerve needle electrode technique in 14 normal volunteers (7 men and 7 women), aged 34.5 ± 14.8 years. The stimulus consisted of rectangular pulses of 0.2-ms duration at a frequency of 1 Hz with an intensity at least 6 times greater than the threshold value for the main component. Five hundred to 2000 sweep averagings were performed. The duration of analysis was 40 or 50 ms and the wave analysis frequency was 200 (-6 dB/oct) to 3000 Hz (-12 dB/oct). We used an apparatus with a two-channel amplifier system, 200 MW or more of entry impedance and a noise level of 0.7 µVrms or less. The main component mean amplitude, conduction velocity and latency and the late component mean amplitude, conduction velocity and latency were respectively (mean ± SD): 26.5 ± 5.42 µV, 56.8 ± 5.42 m/s, 3.01 ± 0.31 ms, 0.12 ± 0.04 µV, 16.4 ± 2.95 m/s and 10.6 ± 2.48 ms. More sophisticated equipment has an internal noise of 0.6 µVrms. These data demonstrate that the technique can now be employed to study thin fiber neuropathies, like in leprosy, using commercial electromyographs, even in non-academic practices

Identification of the main generator source of longitudinal muscle contraction in the earthworm ventral nerve cord

The main generator source of a longitudinal muscle contraction was identified as an M (mechanical-stimulus-sensitive) circuit composed of a presynaptic M-1 neuron and a postsynaptic M-2 neuron in the ventral nerve cord of the earthworm, Amynthas hawayanus, by simultaneous intracellular response recording and Lucifer Yellow-CH injection with two microelectrodes. Five-peaked responses were evoked in both neurons by a mechanical, but not by an electrical, stimulus to the mechanoreceptor in the shaft of a seta at the opposite side of an epidermis-muscle-nerve-cord preparation. This response was correlated to 84% of the amplitude, 73% of the rising rate and 81% of the duration of a longitudinal muscle contraction recorded by a mechano-electrical transducer after eliminating the other possible generator sources by partitioning the epidermis-muscle piece of this preparation. The pre- and postsynaptic relationship between these two neurons was determined by alternately stimulating and recording with two microelectrodes. Images of the Lucifer Yellow-CH-filled M-1 and M-2 neurons showed that both of them are composed of bundles of longitudinal processes situated on the side of the nerve cord opposite to stimulation. The M-1 neuron has an afferent process (A1) in the first nerve at the stimulated side of this preparation and the M-2 neuron has two efferent processes (E1 and E3) in the first and third nerves at the recording side where their effector muscle cell was identified by a third microelectrode.

Use of fluorescent probes to follow membrane traffic in nerve terminals

Optical tracers in conjunction with fluorescence microscopy have become widely used to follow the movement of synaptic vesicles in nerve terminals. The present review discusses the use of these optical methods to understand the regulation of exocytosis and endocytosis of synaptic vesicles. The maintenance of neurotransmission depends on the constant recycling of synaptic vesicles and important insights have been gained by visualization of vesicles with the vital dye FM1-43. A number of questions related to the control of recycling of synaptic vesicles by prolonged stimulation and the role of calcium to control membrane internalization are now being addressed. It is expected that optical monitoring of presynaptic activity coupled to appropriate genetic models will contribute to the understanding of membrane traffic in synaptic terminals.

Early myelin breakdown following sural nerve crush: a freeze-fracture study

In this study we describe the early changes of the myelin sheath following surgical nerve crush. We used the freeze-fracture technique to better evaluate myelin alterations during an early stage of Wallerian degeneration. Rat sural nerves were experimentally crushed and animals were sacrificed by transcardiac perfusion 30 h after surgery. Segments of the nerves were processed for routine transmission electron microscopy and freeze-fracture techniques. Our results show that 30 h after the lesion there was asynchrony in the pattern of Wallerian degeneration, with different nerve fibers exhibiting variable degrees of axon disruption. This was observed by both techniques. Careful examination of several replicas revealed early changes in myelin membranes represented by vacuolization and splitting of consecutive lamellae, rearrangement of intramembranous particles and disappearance of paranodal transverse bands associated or not with retraction of paranodal myelin terminal loops from the axolemma. These alterations are compatible with a direct injury to the myelin sheath following nerve crush. The results are discussed in terms of a similar mechanism underlying both axon and myelin breakdown.

Muscle sympathetic nerve activity and hemodynamic alterations in middle-aged obese women

To study the relationship between the sympathetic nerve activity and hemodynamic alterations in obesity, we simultaneously measured muscle sympathetic nerve activity (MSNA), blood pressure, and forearm blood flow (FBF) in obese and lean individuals. Fifteen normotensive obese women (BMI = 32.5 ± 0.5 kg/m²) and 11 age-matched normotensive lean women (BMI = 22.7 ± 1.0 kg/m²) were studied. MSNA was evaluated directly from the peroneal nerve by microneurography, FBF was measured by venous occlusion plethysmography, and blood pressure was measured noninvasively by an autonomic blood pressure cuff. MSNA was significantly increased in obese women when compared with lean control women. Forearm vascular resistance and blood pressure were significantly higher in obese women than in lean women. FBF was significantly lower in obese women. BMI was directly and significantly correlated with MSNA, blood pressure, and forearm vascular resistance levels, but inversely and significantly correlated with FBF levels. Obesity increases sympathetic nerve activity and muscle vascular resistance, and reduces muscle blood flow. These alterations, taken together, may explain the higher blood pressure levels in obese women when compared with lean age-matched women.

Effects of L-arginine on the diaphragm muscle twitches elicited at different frequencies of nerve stimulation

In rats, the nitric oxide (NO)-synthase pathway is present in skeletal muscle, vascular smooth muscle, and motor nerve terminals. Effects of NO were previously studied in rat neuromuscular preparations receiving low (0.2 Hz) or high (200 Hz) frequencies of stimulation. The latter frequency has always induced tetanic fade. However, in these previous studies we did not determine whether NO facilitates or impairs the neuromuscular transmission in preparations indirectly stimulated at frequencies which facilitate neuromuscular transmission. Thus, the present study was carried out to examine the effects of NO in rat neuromuscular preparations indirectly stimulated at 5 and 50 Hz. The amplitude of muscular contraction observed at the end (B) of a 10-s stimulation was taken as the ratio (R) of that obtained at the start (A) (R = B/A). S-nitroso-N-acetylpenicillamine (200 µM), superoxide dismutase (78 U/ml) and L-arginine (4.7 mM), but not D-arginine (4.7-9.4 mM), produced an increase in R (facilitation of neurotransmission) at 5 Hz. However, reduction in the R value (fade of transmission) was observed at 50 Hz. N G-nitro-L-arginine (8.0 mM) antagonized both the facilitatory and inhibitory effects of L-arginine (4.7 mM). The results suggest that NO may modulate the release of acetylcholine by motor nerve terminals.

Chronic experimental myocardial infarction produces antinatriuresis by a renal nerve-dependent mechanism

The present study focused on the role of sympathetic renal nerve activity, in mediating congestive heart failure-induced sodium retention following experimental chronic myocardial infarction. Groups of male Wistar rats (240-260 g) were studied: sham-operated coronary ligation (CON3W, N = 11), coronary ligation and sham-operated renal denervation (INF3W, N = 19), 3 weeks of coronary ligation and sympathetic renal nerve denervation (INF3WDX, N = 6), sham-operated coronary ligation (N = 7), and 16 weeks of coronary ligation (INF16W, N = 7). An acute experimental protocol was used in which the volume overload (VO; 5% of body weight) was applied for 30 min after the equilibration period of continuous iv infusion of saline. Compared to control levels, VO produced an increase (P < 0.01, ANOVA) in urine flow rate (UFR; 570%) and urinary sodium excretion (USE; 1117%) in CON3W. VO induced a smaller increase (P < 0.01) in USE (684%) in INF3W. A similar response was also observed in INF16W. In INF3WDX, VO produced an immediate and large increase (P < 0.01) in UFR (547%) and USE (1211%). Similarly, in INF3W VO increased (P < 0.01) UFR (394%) and USE (894%). Compared with INF3W, VO induced a higher (P < 0.01) USE in INF3WDX, whose values were similar to those for CON3W. These results suggest that renal sympathetic activity may be involved in sodium retention induced by congestive heart failure. This premise is supported by the observation that in bilaterally renal denervated INF3WDX rats myocardial infarction was unable to reduce volume expansion-induced natriuresis. However, the mechanism involved in urinary volume regulation seems to be insensitive to the factors that alter natriuresis.

The role of the vagus nerve in hypertonic resuscitation of hemorrhagic shocked dogs

Previous studies have suggested a critical role for the vagi during the hypertonic resuscitation of hemorrhagic shocked dogs. Vagal blockade prevented the full hemodynamic and metabolic recovery and increased mortality. This interpretation, however, was challenged on the grounds that the blockade also abolished critical compensatory mechanisms and therefore the animals would die regardless of treatment. To test this hypothesis, 29 dogs were bled (46.0 ± 6.2 ml/kg, enough to reduce the mean arterial pressure to 40 mmHg) and held hypotensive for 45 min. After 40 min, vagal activity was blocked in a reversible manner (0ºC/15 min) and animals were resuscitated with 7.5% NaCl (4 ml/kg), 0.9% NaCl (32 ml/kg), or the total volume of shed blood. In the vagal blocked isotonic saline group, 9 of 9 dogs, and in the vagal blocked replaced blood group, 11 of 11 dogs survived, with full hemodynamic and metabolic recovery. However, in the hypertonic vagal blocked group, 8 of 9 dogs died within 96 h. Survival of shocked dogs which received hypertonic saline solution was dependent on vagal integrity, while animals which received isotonic solution or blood did not need this neural component. Therefore, we conclude that hypertonic resuscitation is dependent on a neural component and not only on the transient plasma volume expansion or direct effects of hyperosmolarity on vascular reactivity or changes in myocardial contraction observed immediately after the beginning of infusion.

Differential role of entorhinal and hippocampal nerve growth factor in short- and long-term memory modulation

We studied the effects of infusion of nerve growth factor (NGF) into the hippocampus and entorhinal cortex of male Wistar rats (250-300 g, N = 11-13 per group) on inhibitory avoidance retention. In order to evaluate the modulation of entorhinal and hippocampal NGF in short- and long-term memory, animals were implanted with cannulae in the CA1 area of the dorsal hippocampus or entorhinal cortex and trained in one-trial step-down inhibitory avoidance (foot shock, 0.4 mA). Retention tests were carried out 1.5 h or 24 h after training to measure short- and long-term memory, respectively. Immediately after training, rats received 5 µl NGF (0.05, 0.5 or 5.0 ng) or saline per side into the CA1 area and entorhinal cortex. The correct position of the cannulae was confirmed by histological analysis. The highest dose of NGF (5.0 ng) into the hippocampus blocked short-term memory (P < 0.05), whereas the doses of 0.5 (P < 0.05) and 5.0 ng (P < 0.01) NGF enhanced long-term memory. NGF administration into the entorhinal cortex improved long-term memory at the dose of 5.0 ng (P < 0.05) and did not alter short-term memory. Taken as a whole, our results suggest a differential modulation by entorhinal and hippocampal NGF of short- and long-term memory.

Trabeculectomy and optic nerve head topography

The objective of the present study was to evaluate changes in optic nerve head parameters, measured by confocal laser tomography, before and after trabeculectomy in order to identify outcome measures for the management of glaucoma. The optic nerve head of 22 eyes (22 patients) was analyzed by confocal laser tomography with the Heidelberg retinal tomogram (HRT) before and after trabeculectomy. The median time between the first HRT and surgery was 4.6 months (mean: 7.7 ± 8.3) and the median time between surgery and the second HRT was 10.8 months (mean: 12.0 ± 6.8). The patients were divided into two groups, i.e., those with the highest (group A) and lowest (group B) intraocular pressure (IOP) change after surgery. Differences in the 12 standard topographic parameters before and after surgery for each group were evaluated by the Wilcoxon signed rank test and the differences in these parameters between the two groups were compared by the Mann-Whitney rank sum test. Multiple regression analysis was used to evaluate the influence of the change in IOP (deltaIOP and deltaIOP%) and the changes in the other parameters. There were significant differences in the HRT measures before and after surgery in group A only for cup volume. In group B, no parameter was statistically different. The changes in group A were not significantly different than those in group B for any parameter (P > 0.004, Bonferroni correction for multiple comparisons). deltaIOP and deltaIOP% had a statistically significant effect on delta cup disk area, delta cup volume and delta mean cup depth. Changes in cup shape size were influenced significantly only by deltaIOP. Some optic disc parameters measured by HRT presented a significant improvement after filtering surgery, depending on the amount of IOP reduction. Long-term studies are needed to determine the usefulness of these findings as outcome measures in the management of glaucoma.

Role of the cardiac nerve in the effect of a novel innocuous stimulus on the heart rate of Megalobulimus mogianensis

The effects of a brief jet of water delivered to the anterior portion of body-head on the heart rate of Megalobulimus mogianensis were determined in a group of intact snails (N = 8), previously prepared for electrocardiogram recording. The heart rate was significantly increased following stimulation. Nevertheless, with repetition of the stimulus there was a significant decrease in the magnitude of the heart rate variation and in the time for the basal heart rate to recover (first stimulus, 7.4 ± 1.2 bpm and 15.5 ± 1.8 min; second stimulus, 4.8 ± 1.0 bpm and 10.6 ± 1.5 min; third stimulus, 5.0 ± 0.3 bpm and 11.1 ± 1.8 min), indicating that this behavioral response undergoes early habituation. To determine the role of the cardiac nerve in mediating the heart rate alterations induced by the jet of water two other groups were tested: denervated animals (N = 8) and sham-operated control animals (N = 8). Although the innocuous stimulus caused the heart rate to increase significantly in both experimental groups, the mean increase in heart rate in denervated animals (3.2 ± 0.4 bpm) was 41% of the value obtained in sham-operated animals (7.8 ± 1.5 bpm), indicating that the cardiac nerve is responsible for 59% of the cardioacceleration induced by the innocuous stimulus. The increase in heart rate observed in denervated animals may be due to an increase in venous return promoted by the intense muscular activity associated with the retraction-protraction of the anterior part of the body induced by the jet of water.

Does acute hyperglycemia alter rat aortic depressor nerve function?

Because it is not known where in the reflex arch, i.e., afference, central nervous system or efferences, hyperglycemia affects baroreflex function, the present study examined the effect of short-term (30 min) hyperglycemia on aortic depressor nerve function measured by a mean arterial pressure vs aortic depressor nerve activity curve, fitted by sigmoidal regression, or by cross-spectral analysis between mean arterial pressure and aortic depressor nerve activity. Anesthetized male Wistar rats received an intravenous bolus (0.25 mL) injection, followed by 30 min of infusion (1 mL/h) of 30% glucose (N = 14). Control groups received a bolus injection and infusion of 0.9% saline (N = 14), or 30% mannitol (N = 14). Glucose significantly increased both blood glucose and plasma osmolarity (P < 0.05). Mean arterial pressure did not change after glucose, saline or mannitol infusion. Mean arterial pressure vs nerve activity curves were identical before and 10 and 30 min after the beginning of glucose, saline or mannitol infusion. Slow (0.3 Hz) oscillations of arterial pressure were induced by controlled bleeding, and cross-spectral analysis was applied to arterial pressure and aortic nerve activity. Transfer function magnitude (aortic depressor nerve activity/mean arterial pressure ratio in the frequency domain) was calculated as an index of gain of the aortic depressor nerve. Transfer function magnitude was similar in all groups during induced or spontaneous oscillations of arterial pressure. In conclusion, the present study demonstrates, by means of two different approaches for assessing baroreceptor function, that aortic depressor nerve activity was not altered by short-term (30 min) hyperglycemia.