S1-S3 Segments Research Articles

Axial heterogeneity of superficial proximal tubule paracellular transport in mice.

A considerable amount of NaCl reabsorption in proximal tubules (PTs) occurs via the paracellular transport regulated by the tight junction proteins claudins (Cldns). However, the paracellular transport properties in mouse superficial PTs remain unclear. We characterized these properties in superficial PT S1-S3 segments from mice expressing [wild-type (WT, WTS1-WTS3)] or lacking claudin-2 [knockout (KO, KOS1-KOS3)]. We isolated and perfused segments with symmetrical solutions in the presence of bath ouabain and measured the diffusion potential upon changing the salt composition of the lumen or bath. Based on the diffusion potential corrected for the liquid junction potential (dVT), we calculated the paracellular Na+ over Cl- permeability (PNa/PCl) ratio. The PNa/PCl values upon reducing luminal NaCl averaged 1.27, 1.04, and 0.85 in WTS1, WTS2, and WTS3 and 0.34, 0.55, and 0.80 in KOS1, KOS2, and KOS3, respectively. The dVT values exhibited a symmetrical response to bidirectional NaCl concentration gradients in WTS1-WTS3 and KOS1-KOS3. WTS1 and WTS3 were monovalent cation-selective, with WTS1 demonstrating stronger cation selectivity. The order of permeabilities relative to Cl- was K+ > Rb+ > Na+ > Li+, whereas both KOS1 and KOS3 exhibited monovalent cation selectivity loss and consequently enhanced anion selectivity, especially in KOS1. Protamine addition to the lumen and bath similarly decreased PNa/PCl values upon reduced luminal NaCl in the order of WTS1 > WTS3 > KOS3 > KOS1. Therefore, this study presents evidence of axial heterogeneity in paracellular transport across superficial PTs in mice.

Right sleeve S2 segmentectomy for lung carcinoid tumor in a patient with tracheal bronchus.

Carcinoid tumors are relative rare neuroendocrine tumors of the lung. Bronchial obstruction's symptoms as cough, hemoptysis and pneumonia may be present when they are centrally located and lung-sparing surgery is usually preferred. We describe the case of an adult patient with a central right upper lobe carcinoid tumor and a concurrent tracheal bronchus malformation. This peculiar bronchial malformation allowed a sleeve S2 segmentectomy sparing the S1-S3 segments and the middle and lower lobes. The patient was discharged on day 4 without complications.

Classifications in Brief: The Denis Classification of Sacral Fractures.

Classifications in Brief: The Denis Classification of Sacral Fractures.

Striated Perineal Muscles: Location of Somatic and Autonomic Neurons Projecting to the Male Pig Ischiocavernous Muscle. Neurochemical Features of the Sympathetic Subset.

The location, number and size of the central and peripheral neurons innervating the ischiocavernous muscle (ICM) were studied in male pigs by means of Fast Blue (FB) retrograde neuronal tracing. Moreover the immunohistochemical properties of the sympathetic ganglia were investigated combining the double immunolabeling method. After injection of FB into the left ICM, a mean number of 245.3 ± 134.9 labeled neurons were found in the ipsilateral ventral horn of the S1-S3 segments of the spinal cord (SC), 129.7 ± 45.5 in the L6-S3 ipsilateral and S2-S3 contralateral spinal ganglia (SGs), 2279.3 ± 622.1 in the ipsilateral L2-S2 and contralateral L5-S2 sympathetic trunk ganglia (STGs), 541.7 ± 158 in the bilateral caudal mesenteric ganglia (CMGs), and 78.3 ± 35.8 in the microganglia of the pelvic plexus (PGs). The mean area of the ICM projecting neurons was 1217 ± 69.7 μm2 in the SC, 2737.5 ± 176.5 μm2 in the SGs, 982.8 ± 36.8 μm2 in the STGs, 865.9 ± 39.14 μm2 in the CMGs and 426.2 ± 24.72 μm2 in the PGs. The FB positive neurons of autonomic ganglia contained Dopamine β hydroxylase, vesicular acetylcholine transporter, neuronal nitric oxyde sinthase, calcitonine gene related peptide, leu-enkephaline, neuropeptide Y, substance P, vasoactive intestinal polypeptide, and somatostatine often colocalized with tyrosine hydroxylase. The particular localization of the motor somatic nucleus, the abundant autonomic innervation and the qualitatively different content of ICM projecting sympathetic neurons suggest a complex regulation of this striated muscle involved in involuntary functions, such as the erection, ejaculation, micturition and defecation. Anat Rec, 301:837-848, 2018. © 2017 Wiley Periodicals, Inc.

Diabetes, hypertension, and chronic kidney disease progression: role of DPP4.

The protein dipeptidyl peptidase 4 (DPP4) is a target in diabetes management and reduction of associated cardiovascular risk. Inhibition of the enzymatic function and genetic deletion of DPP4 is associated with tremendous benefits to the heart, vasculature, adipose tissue, and the kidney in rodent models of obesity, diabetes and hypertension, and associated complications. The recently concluded, "Saxagliptin Assessment of Vascular Outcomes Recorded in Patients with Diabetes Mellitus-Thrombolysis in Myocardial Infarction 53" trial revealed a reduction in proteinuria in chronic kidney disease patients (stages 1-3). These results have spurred immense interest in the nonenzymatic and enzymatic role of DPP4 in the kidney. DPP4 is expressed predominantly in the glomeruli and S1-S3 segments of the nephron and to a lesser extent in other segments. DPP4 is known to facilitate absorption of cleaved dipeptides and regulate the function of the sodium/hydrogen exchanger-3 in the proximal tubules. DPP4, also known as CD26, has an important role in costimulation of lymphocytes via caveolin-1 on antigen-presenting cells in peripheral blood. Herein, we present our perspectives for the ongoing interest in the role of DPP4 in the kidney.

Computational Characterization of Conformational Transitions in the Voltage-Sensing Domain of Ci-VSP

The canonical voltage-sensing domain (VSD) is a conserved structural module that transduces the electric field across cellular membranes into defined protein motions of its charge-rich helix, the S4 segment. Up on depolarization, the VSD rearranges from the ‘resting’ (or ‘down’) state conformation into the ‘active’ (or ‘up’) state conformation, which in turn regulates the motion of downstream modules of the protein, such as opening of the pore domain of a voltage-gated ion channel or the activity of an enzyme. The voltage-sensing process has long attracted much interest and fruitful results have been reported using a variety of functional, spectroscopic and structural approaches. Recently, we solved crystal structures of the VSD of the Ciona intestinalis voltage-sensing phosphatase Ci-VSP in both it resting (Down) and activated (Up) conformations. Comparison of the two structures reveals an ∼ 5-A three-residue displacement of the S4 segment along, together with an ∼ 60° rotation around, its axis (called the one-click gating motion), while the S1-S3 segments remain fairly stable. Using 2-D self-learning umbrella sampling molecular dynamics simulations, combined with homology modeling and the string method, we have now calculated the free energy landscape governing the conformational changes of Ci-VSD. These calculations have allowed us to explore the energetic viability of further up (one-click up) and further down (two-clicks down) conformations, as potential mechanisms for additional charge translocation. These conformations should advance our understanding of the detailed mechanisms of voltage-gating and allow for the design of new experiments aimed to verify the present model of S4 movements and gating charge translocation.

Offsetting the Electric Field Sensed by KV Channels through Residue Substitutions on Top of S1

Kv channel subunits consist of 6 transmembrane segments (S1-S6) whereby the S1 through S4 segments assemble into a voltage sensing domain (VSD) that detects the membrane electric field. The positively charged S4 segment forms the main component of the VSD and undergoes the largest reorientations upon a membrane de- or hyperpolarization, generating a transient gating current. The S1-S3 segments surround the S4 and facilitate the latter's movement across the hydrophobic plasma-membrane. A positive (lysine) and negative (aspartate) charge substitution scan at the extracellular end of the S1 segment in the Shaker-type Kv1.5 channel indicated that this region is sufficiently close to the S4 segment such that it modulates the local membrane electric field. At positions E268, E272, F273 and E276 a charge substitution or charge introduction exerted a surface charge effect and shifted the voltage dependence of channel opening accordingly. Surprisingly, these residues, which modulated the electric field, did not face the S4 in a predicted 3D structure of the Kv1.5 channel in the open state (homology model based on the crystal structure of the Kv2.1/Kv1.2 chimera). This suggests that the introduced charges affect the electrical field around the S4 segment in the closed state only. In conclusion, residues at the top of the S1 segment can state-dependently offset (polarize) the electric field sensed by the S4 segment, supporting that both segments are in close proximity. (This research was supported by fellowship CONACyT #203936 to EMM & grant FWO-G.0449.11N to DJS.)

Precise comparison of protein localization among OCT, OAT, and MATE in human kidney

Organic anion transporters (OATs) and organic cation transporters (OCT) play pivotal roles in the uptake of drugs into epithelial cells at the basolateral membranes, and multidrug and toxin extrusion (MATE) mediates drug secretion into urine at the brush-border membranes. In this study, the expression and distribution of apical MATE1 and MATE2-K, and basolateral OAT1, OAT3, and OCT2 were compared using serial sections of human kidney cortex. First, mRNA expression in the proximal tubules was evaluated using laser microdissection. Levels of OAT, OCT2, and MATE mRNA in the proximal tubules were greatly higher compared with glomerulus. The results quantitatively indicated that these transporters were localized to proximal tubules in the renal cortex. Second, MATE1 and MATE2-K protein were detected in proximal epithelial cells in which OCT2 protein was expressed at the basolateral membranes. In addition, MATE1 was expressed at the brush-border membranes of tubular epithelial cells in which OAT1 and OAT3 were expressed. The results confirmed that OAT1, OAT3, OCT2, MATE1, and MATE2-K were coexpressed in tubular epithelial cells. The cooperation among OAT, OCT, and MATE in renal drug secretion was consistent with their distribution.

Sacral sparing in SCI: beyond the S4–S5 and anorectal examination

Sensory and/or motor function sparing, including the S4-S5 spinal cord segment, is central to classifying neurologic impairment after spinal cord injury (SCI) using the American Spinal Injury Association Impairment Scale (AIS) grades within the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI). Within the ISNCSCI protocol, which is essential for both clinical and research purposes, assessing sacral sparing requires an anorectal and S4-S5 examination. However, in situations where these data are incomplete, the relationships between anorectal/S4-S5 examinations and functional preservation at more rostral sacral segments may be useful. To evaluate whether slightly more rostral sensory and motor outcomes of the ISNCSCI can accurately predict caudal sacral sparing (S4-S5 dermatome sensation, "deep pressure" anal sensation [AS], and voluntary anal contraction [AC]). Retrospective analysis of the European Multicenter Study about Spinal Cord Injury database. One thousand four hundred sixty-seven AIS-A, AIS-B, and AIS-C subjects. International Standards for Neurological Classification of Spinal Cord Injury examinations. The value of six factors (sensory preservation at S1, S2, and S3; motor preservation at S1; motor function at more than three segments below the motor level; and sensory function at more than three segments below the neurologic level) for predicting ISNCSCI sacral sparing measures (AS, S4-S5 dermatome sensation, AC) was evaluated. Combinations of the most promising factors were then evaluated for their ability to accurately predict the AIS grade. Preserved sensation at the first sacral segment (S1S) provided good prediction (90.5%) of caudal sacral sensory sparing (ie, AS or S4-S5 sensation). Voluntary anal contraction was accurately predicted by preserved motor function within the first sacral segment (S1M) in 85.4% of cases. The alternate classification schemes evaluated for accurately predicting the AIS classification grade were S1S+S1M and S1S+motor preservation more than three segments below the motor level. The ability of these schemes to accurately predict AIS grades was stable over time but varied with the rostrocaudal level of spinal injury. For the initial baseline examination, the alternate classification schemes were accurate in ~95% of cases for T2-T9 SCI, with slightly lower accuracy for cervical SCI (~80%). There are close relationships between functional sparing at different sacral segments. These relationships can be used to estimate AIS grades when complete information about the anorectal and S4-S5 examination is not available. The accuracy of the classification remains stable over time, while the increased variability in lower levels of SCI, that is, lumbar injuries, emphasizes the importance of careful sacral examinations. The highly reliable predictive values of S1-S3 segments can complement conclusions from anorectal examinations if the latter are considered to be confounded or incomplete.

Voltage Sensor Module in NaV1.4: S1-S3 Charges Regulate Fast Inactivation

We investigated the role of charged amino acid residues in the extracellular (ENC) and intracellular (INC) clusters of S1-S3 segments for each of four domains in skeletal muscle sodium channel NaV1.4. We used charge reversing and substituting mutations to show that the extracellular cluster of negative charge in domains III and IV promotes fast inactivation and limits its recovery. E1051R (S1) and D1069K (S2) in domain II slowed entry of channels into fast inactivation and accelerated recovery; E1051D and D1069E each rescued wild type fast inactivation parameters. In domain IV, destabilization of the fast-inactivated state by E1373K (S1) was not rescued in the E1373N mutation, whereas charge-dependent destabilization of fast inactivation was observed with mutations at N1389 (S2). Mutations within the ENC of domains I and II produced lesser effects on fast inactivation, but did inhibit activation. Effects on charge reversing mutations within the INC included an increase in the probability of fast inactivation from closed states. Homology models of the voltage sensor module of each domain were constructed from alignment of sequences of hNaV1.4 to NaVAb, using Modeller. Homology models were constructed for S1 through S4-S5 linker regions, basing the models on the data inferred from the crystal structure of the bacterial sodium channel (Payandeh et al., 2011). The models for hNaV1.4 voltage sensor module in domains I to IV support the hypothesis that S1-S3 counter charges influence the movement of S4 during activation and may explain the effects of mutations in these segments to regulate fast inactivation in a mammalian sodium channel.

Direct projections from the sacral spinal cord to the medial preoptic area in cat and guinea pig

The medial preoptic area (MPO) plays an important role in many behavioral, autonomic and endocrine functions, including micturition and genital responses. Although afferents of the MPO have been studied extensively, it is unknown whether direct lumbosacral-MPO projections exist that could convey afferent information from the pelvic organs. We hypothesized that, if such direct projections exist, MPO projecting cells would be located in the lateral part of the sacral cord, where primary afferents from pelvic and pudendal nerves terminate. We used retro- and anterograde tracing techniques in cat and guinea pig to study this. In cats, injections in the MPO resulted in labeled cells throughout the spinal cord, but with the highest density in the S1–S2 segments. In guinea pigs, labeled cells were found exclusively in the S1–S3 segments after MPO injections. Labeled cells in the sacral segments were not located in the lateral parts of the gray matter, but were found in the medial laminae VI–VII and dorsal lamina VIII in cats, and mainly in lamina X in guinea pigs. Anterograde tracing results after injections in the sacral cord in cats or guinea pigs showed labeled fibers in the MPO, just ventral to the anterior commissure. The central location of the cells of origin within the sacral cord, together with the termination pattern of the spino-MPO projections, strongly suggest a role for the spino-MPO pathway in the sensory relay of pelvic viscera, important for micturition and genital responses.

Striated Perineal Muscles: Location of Autonomic, Sensory, and Somatic Neurons Projecting to the Male Pig Bulbospongiosus Muscle

The location, number, and size of the neurons innervating the bulbospongiosus muscle (BSM) were studied in male pigs, by means of Fast Blue (FB) retrograde transport. After injection of FB into the left BSM, labeled neurons were found bilaterally in the L2-S4 sympathetic trunk ganglia (STGs), in the caudal mesenteric ganglia (CMGs), in the microganglia of the pelvic plexus (PGs), in a dorsolateral area with respect to the central canal of S1-S3 segments of the spinal cord (SC) and in the S1-S4 ipsilateral and S2-S3 contralateral spinal ganglia (SGs). The mean number of labeled FB cells was 3,122 +/- 1,968 in STGs, 979 +/- 667 in CMGs, 108 +/- 104 in PGs, 89 +/- 39 in SC and 77 +/- 23 in SGs. The area of the multipolar neurons was 852 +/- 22 microm(2) in the STGs, 878 +/- 23 microm(2) in the CMGs and 922 +/- 31 microm(2) in the PGs. The multipolar SC neurons had an area of 1,057 +/- 38 microm(2), while pseudounipolar SG cells had dimensions of 2,281 +/- 129 microm(2). Our research enables us to highlight two peculiarities regarding the innervation of the boar BSM: the very high number of labeled autonomic neurons and the particular localization of the motor somatic nucleus.

Dynamic MR Based Analysis of Tumor Movement in Upper and Mid Lobe Localized Lung Cancer

Tumor motion is a very important factor in the radiotherapy of lung cancer. Uncertainty resulting from tumor movement must be considered in 3D therapy planning especially in case of IMRT or stereotactic therapy. The aim of our dynamic MR based study was to detect tumor movements in upper and mid lobe lung tumors. Twenty-four patients with newly diagnosed stage II-IV lung cancer were enrolled into the study. According to tumor localization in the right S1-S3 segments 9, in the right S4-S6 segments 2, in the left S1-S3 segments 9 and in the left S4-S6 segments 4 lesions were detected. In normal treatment position individual dynamic MR examinations were performed in axial, sagittal and coronal planes (100 slices/30 sec). For tumor motion analysis E-RAD PAC's software was used. Movements of the tumor under normal breathing conditions were registered in the three main directions. The mean antero-posterior deviation was 0,109 cm (range: 0,063 cm-0,204 cm), the mean medio-lateral deviation was 0,114 cm (range: 0,06 cm- 0,244 cm). The greatest deviation was measured in cranio-caudal direction (mean: 0,27 cm, range: 0,079 cm- 0,815 cm). The mean direction independent deviation was 0,18 cm (range: 0,09 cm- 0,48 cm). Dynamic MR is a sensitive and well tolerated method for tumor motion monitoring in high precision 3D therapy planning of lung cancer patients. Our results demonstrate that tumors located in the upper and mid lobes have moderate breath synchronous movements. The greatest deviation occur in cranio-caudal direction.

Novel NaPi-2c mutations that cause mistargeting of NaPi-2c protein and uncoupling of Na-Picotransport cause HHRH

hereditary hypophosphatemic rickets with hypercalciuria (HHRH) is an autosomal recessive inherited disorder of mineral and bone metabolism. It is characterized by hypophosphatemia, rickets, and increased serum 1,25-dihydroxyvitamin D concentration, resulting in secondary absortive hypercalciuria and

Voltage sensor conformations in the open and closed states in ROSETTA structural models of K(+) channels.

Voltage-gated ion channels control generation and propagation of action potentials in excitable cells. Significant progress has been made in understanding structure and function of the voltage-gated ion channels, highlighted by the high-resolution open-state structure of the voltage-gated potassium channel, K(v)1.2. However, because the structure of the closed state is unknown, the gating mechanism remains controversial. We adapted the rosetta membrane method to model the structures of the K(v)1.2 and KvAP channels using homology, de novo, and domain assembly methods and selected the most plausible models using a limited number of experimental constraints. Our model of K(v)1.2 in the open state is very similar in overall topology to the x-ray structure of this channel. Modeling of KvAP in the open state suggests that orientation of the voltage-sensing domain relative to the pore-forming domain is considerably different from the orientation in the K(v)1.2 open state and that the magnitude of the vertical movement of S4 is significantly greater. Structural modeling of closed state of K(v)1.2 suggests gating movement that can be viewed as a sum of two previously suggested mechanisms: translation (2-4 A) plus rotation ( approximately 180 degrees ) of the S4 segment as proposed in the original "sliding helix" or "helical screw" models coupled with a rolling motion of the S1-S3 segments around S4, similar to recent "transporter" models of gating. We propose a unified mechanism of voltage-dependent gating for K(v)1.2 and KvAP in which this major conformational change moves the gating charge across the electric field in an analogous way for both channels.

Cauda equina syndrome and nitric oxide synthase immunoreactivity in the spinal cord of the dog

The development of the cauda equina syndrome in the dog and the involvement of spinal nitric oxide synthase immunoreactivity (NOS-IR) and catalytic nitric oxide synthase (cNOS) activity were studied in a pain model caused by multiple cauda equina constrictions. Increased NOS-IR was found two days post-constriction in neurons of the deep dorsal horn and in large, mostly bipolar neurons located in the internal basal nucleus of Cajal seen along the medial border of the dorsal horn. Concomitantly, NOS-IR was detected in small neurons close to the medioventral border of the ventral horn. High NOS-IR appeared in a dense sacral vascular body close to the Lissauer tract in S1-S3 segments. Somatic and fiber-like NOS-IR appeared at five days post-constriction in the Lissauer tract and in the lateral and medial collateral pathways arising from the Lissauer tract. Both pathways were accompanied by a dense punctate NOS immunopositive staining. Simultaneously, the internal basal nucleus of Cajal and neuropil of this nucleus exhibited high NOS-IR. A significant decrease in the number of small NOS immunoreactive somata was noted in laminae I-II of L6-S2 segments at five days post-constriction while, at the same time, the number of NOS immunoreactive neurons located in laminae VIII and IX was significantly increased. Moreover, high immunopositivity in the sacral vascular body persisted along with a highly expressed NOS-IR staining of vessels supplying the dorsal sacral gray commissure and dorsal horn in S1-S3 segments. cNOS activity, based on a radioassay of compartmentalized gray and white matter regions of lower lumbar segments and non-compartmentalized gray and white matter of S1-S3 segments, proved to be highly variable for both post-constriction periods.

Distribution of NADPH-d and nNOS-IR in the thoracolumbar and sacrococcygeal spinal cord of the guinea pig

The distribution of NADPH-d staining and neuronal nitric oxide synthase (nNOS)-immunoreactivity in the spinal cord of the guinea pig was studied to evaluate the potential role of nitric oxide in lumbosacral afferent and spinal autonomic pathways and to compare the distribution of these two markers to that observed in other species. NADPH-d staining and nNOS-immunoreactivity were present in neurons and fibers in the superficial dorsal horn, dorsal commissure and in neurons around the central canal in all levels of the spinal cord examined. Sympathetic preganglionic neurons in the thoracic and rostral lumbar segments identified by choline acetyl transferase (ChAT) immunoreactivity exhibited prominent NADPH-d staining and nNOS-immunoreactivity; whereas the ChAT-immunoreactive parasympathetic preganglionic neurons in the sacral segments were not stained. The most prominent NADPH-d staining in the sacral segments occurred in fibers extending from Lissauer's tract through laminae I along the lateral edge of the dorsal horn to the region of the sacral parasympathetic nucleus (lateral collateral pathway of Lissauer). These fibers were prominent in the S1–S3 segments but not in adjacent (L5–L7 and Cx1) or thoracolumbar segments. These NADPH-d fibers were, for the most part, not nNOS-immunoreactive, but did overlap with a prominent fiber bundle containing vasoactive intestinal polypeptide immunoreactivity in the sacral spinal cord. These results indicate that nitric oxide may function as a transmitter in thoracolumbar sympathetic preganglionic neurons, but not in sacral parasympathetic preganglionic neurons. Although the functional significance of the NADPH-d positive, nNOS-negative fiber bundle on the lateral edge of the sacral dorsal horn remains to be determined, this fiber tract may represent, in part, visceral afferent projections to the sacral parasympathetic nucleus.

Distribution of the sacral neurones of origin of the ascending spinal tracts with axons passing through the lateral funiculi of the lowermost thoracic segments: an experimental HRP study in the cat.

The locations of 249 cell bodies of the ascending tract neurones in the grey matter of S1-S3 segments of the spinal cord were reconstructed by histochemical staining, after their axons (or axonal collaterals) at the level of the Thl3 segment were injected with horseradish peroxidase (HRP). In three cats in which the injections of HRP were restricted to the lateral part of the lateral funiculi (llf), about 84% of 159 retrogradely labelled cells were found on the contralateral side, while about 16% were located ipsilaterally. They were the most numerous in S2, S3 and S1 segments, respectively, and the neurones were distributed mainly in the lateral laminae I-VII, medial laminae V, VI and lamina VIII. In three other animals in which the injections of the marker were limited to the dorsal part of the lateral funiculi (dlf), 84 of the 90 ascending tract neurones were found to be distributed in the S2 and S3 segments both ipsi- (lateral laminae III-V) and contralaterally, (lateral laminae IV and V as well as the medial laminae VII and VIII) in similar numbers. The remaining six of the 90 cells with only contralateral projections at the dorsolateral funiculus at Thl3 were scattered within the S1 segment. These data are consistent with the results of studies on sacral spinocerebellar, spinothalamic and spinoreticular projections, as well as the localization of sacral spinocervical and priopriospinal neurones. They may also imply the importance of the bilateral fiber course of the neurones of origin of ascending tracts in the S2 and S3 segments within the dorsolateral funiculus.

Localization of NADPH diaphorase in the thoracolumbar and sacrococcygeal spinal cord of the dog

The distribution of NADPH-d activity and NOS-immunoreactivity in the spinal cord of the dog was studied to evaluate the role of nitric oxide in lumbosacral afferent and spinal autonomic pathways. At all levels of the spinal cord examined, NADPH-d staining and NOS-immunoreactivity were present in neurons and fibers in the superficial dorsal horn, dorsal commissure and in neurons around the central canal. Sympathetic preganglionic neurons in the rostral lumbar segments identified by choline acetyl transferase (ChAT) immunoreactivity exhibited prominent NADPH-d and NOS-immunoreactive staining; whereas the ChAT-immunoreactive parasympathetic preganglionic neurons in the sacral segments were not stained. The most prominent NADPH-d activity in the sacral segments occurred in fibers extending from Lissauer's tract through lamina I along the lateral edge of the dorsal horn to the region of the sacral parasympathetic nucleus. These fibers were prominent in the S1–S3 segments but not in adjacent segments (L5–L7 and Cx1) or in thoracolumbar segments. The NADPH-d fibers were not NOS-immunoreactive, but did overlap with a prominent fiber bundle containing vasoactive intestinal polypeptide immunoreactivity in the sacral spinal cord. These results indicate that nitric oxide may function as a transmitter in thoracolumbar sympathetic preganglionic neurons, but not in sacral parasympathetic preganglionic neurons. The functional significance of the NADPH-d positive, NOS-negative fiber bundle on the lateral edge of the sacral dorsal horn remains to be determined. However, based on anatomical studies in other species it seems reasonable to speculate that the fiber tract represents, in part, visceral afferent projections to the sacral parasympathetic nucleus.

Multiple protracted cauda equina constrictions cause deep derangement in the lumbosacral spinal cord circuitry in the dog

Neuropathological changes of the neuronal pools and spinal cord circuitry in the lumbosacral segments were studied in a canine model of multiple protracted cauda equina constrictions. Anterograde degeneration of all sacrococcygeal and L7 dorsal root fibers was detected in S1–S3 and lower lumbar segments. A narrow degenerated gracile fascicle was found in all thoracic and cervical segments terminating in the gracile nucleus. Transneuronal degeneration of middle-sized and large neurons, located in S1–S3 and sporadically in L7 segments, was noted. Identical transneuronal degeneration was seen in a group of small neurons located in the ventralmost part of lamina VII in S1–S3 segments. Simultaneously, a terminal degeneration was detected in the lateral cervical nucleus and in the ventral posterior lateral nucleus of the ventrobasal thalamic complex. Concomitantly, a fully developed retrograde degeneration affecting motoneurons in the ventrolateral portion of the anterior horn in S1–S3 segments appeared.