2 types of neuromuscular junction in the pharyngeal retractor muscle of snails

The pharyngeal retractor muscle of Helix lucorum is innervated by two symmetrical nerves which contain axons of two types forming myoneural junctions with the muscle cells. Type I junctions correspond to thick axons. These axon terminals which contain a large number of spherical, clear vesicles (41 +/- 5 nm) and a smaller number of dense-cored vesicles (67 +/- 3 nm) make contacts mainly with noncontractile sarcoplasmic processes of muscle cells. Type II junctions correspond to thin axons containing many of granules. Their axon terminals contact with contractile parts of muscle cells and contain a heterogenous population of vesicles: small spherical clear vesicles (44 +/- 2 nm), dense-cored vesicles and numerous irregularly outlined granules with fine-granular content (135 +/- 5 nm). Space between muscle cell is usually wide (50 nm and more) with the exception of sarcoplasmic processes where the gap may be less than 10 nm.     

Efficacy of octreotide in diarrhoea due to Vibrio cholerae: a randomized, controlled trial

The ultrastructure of autonomic nerve fibers and terminal varicosities is described in relation to the lamina propria of the human seminiferous tubules during childhood (age 3 to 10 years). Autonomic nerve varicosities are classified as: Type I with numerous small (30-60 nm) agranular vesicles and variable numbers of large (100 nm) granular vesicles, and Type II with numerous small (30-60 nm) granular vesicles and sporadic large granular vesicles. These two varicosity types are consistent in morphology with cholinergic and adrenergic nerve terminals, respectively. Nerve varicosities are found, associated with Schwann cells, in proximity to the cells of the lamina propria. Although not found in direct "synaptic' contact, these autonomic endings are often within a few hundred nanometers of the cellularity of the lamina propria. The Schwannian sheath is interrupted over the varicosities at these sites and occasionally the terminal varicosities are totally lacking a Schwann sheath. These findings are consistent with the structural relationship of autonomic nerve "terminals' and effector in other endocrine and non-endocrine systems. This is the first evidence of adrenergic nerve varicosities in proximity to the lamina propria in humans (at any age). Evidence is also presented which suggests a locational difference in the distribution of cholinergic (Type I) and adrenergic (Type II) nerve varicosities in this region, with only cholinergic endings observed directly adjacent to the basal lamina of the seminiferous tubules.     

Distribution of the perivascular nerve Ca2+ receptor in rat arteries

We recently showed that perivascular sensory nerves of mesenteric branch arteries express a receptor for extracellular Ca2+ (CaR), and reported data indicating that this CaR mediates relaxation induced by physiologic levels of Ca2+. We have now tested whether the perivascular sensory nerve CaR-linked dilator system is a local phenomenon restricted to the mesentery, or is present in other circulations. Vessels from the mesenteric, renal, coronary, and cerebral circulations were studied. Immunocytochemical analysis was performed using anti-CaR and anti-neural cell adhesion molecule (NCAM) antibodies. Wire myography was used to assess contraction and relaxation. Although perivascular nerves of all arteries stained for CaR protein, there were regional differences. A morphometric method used to estimate CaR positive nerve density revealed the following rank order: mesenteric branch artery > basilar artery = renal interlobar artery > main renal trunk artery > left anterior descending coronary artery. Vessels from the mesentery, renal, coronary, and cerebral circulations showed nerve-dependent relaxation in response to electrical field stimulation (EFS) when precontracted with serotonin in the presence of guanethidine. The degree of Ca2+-induced relaxation of mesenteric, renal, and cerebral arteries positively correlated with the magnitude of EFS-induced relaxation. In contrast, coronary arteries contracted at Ca2+ levels between 1.5 and 3 mmol L(-1), and relaxed to a small degree to 5 mmol L(-1) Ca2+. Thus, a functional perivascular sensory nerve CaR-linked dilator system is present to varying degrees in the mesenteric, renal, and cerebral circulations, but only to a very limited extent in the coronary circulation.     

Three-dimensional structure and composition of CA3-->CA1 axons in rat hippocampal slices: implications for presynaptic connectivity and compartmentalization

Physiological studies of CA3-->CA1 synaptic transmission and plasticity have revealed both pre- and postsynaptic effects. Understanding the extent to which individual presynaptic axonal boutons could provide local compartments for control of synaptic efficacy and microconnectivity requires knowledge of their three-dimensional morphology and composition. In hippocampal slices, serial electron microscopy was used to examine a nearly homogeneous population of CA3-->CA1 axons in the middle of stratum radiatum of area CA1. The locations of postsynaptic densities (PSDs), vesicles, and mitochondria were determined along 75 axon segments (9.1 +/- 2.0 micrometer in length). Synapses, defined by the colocalization of PSDs and vesicles, occurred on average at 2.7 micrometer intervals along the axons. Most varicosities (68%) had one PSD, 19% had 2-4 PSDs, and 13% had none. Synaptic vesicles occurred in 90% of the varicosities. One-half (53%) of the varicosities lacked mitochondria, raising questions about their regulation of ATP and Ca2+, and 8% of varicosities contained only mitochondria. Eleven axons were reconstructed fully. The varicosities were oblong and varied greatly in both length (1.1 +/- 0.7 micrometer) and volume (0.13 +/- 0.14 micrometer 3), whereas the intervaricosity shafts were narrow, tubular, and similar in diameter (0.17 +/- 0.04 micrometer) but variable in length (1.4 +/- 1.2 micrometer). The narrow axonal shafts resemble dendritic spine necks and thus could promote biochemical compartmentalization of individual axonal varicosities. The findings raise the intriguing possibility of localized differences in metabolism and connectivity among different axons, varicosities, and synapses.     

An ultrastructural study of the relationship between sensory trigeminal nerves and odontoblasts in rat dentin/pulp as demonstrated by the anterograde transport of wheat germ agglutinin-horseradish peroxidase (WGA-HRP)

Because the ultrastructure of the trigeminal sensory nerves in dentin, especially in relation to odontoblasts, remains to be clarified, we investigated the relationship between the trigeminal sensory nerves and the odontoblast processes using the anterograde axonal transport technique by injecting wheat germ agglutinin-horseradish peroxidase (WGA-HRP) into the rat trigeminal ganglion. Light microscopically, the nerves labeled with WGA-HRP were mainly concentrated at the pulpal horn, forming a nerve plexus at the subodontoblastic region and penetrating the predentin/dentin about 50 to 70 microns. Ultrastructurally, HRP reaction products were observed intra-axonally in the myelinated (A delta) and unmyelinated (C) axons in the subodontoblastic region. Most nerves lost the Schwann sheath and were naked in the predentin/dentin. The labeled varicosities were close to the odontoblast processes in the dentinal tubules. No synaptic structures could be detected between the varicosities and the odontoblasts, but a gap about 20 nm wide was found between them. One type of varicosity was a rich mitochondria-containing varicosity, while the other was a rich vesicle-containing (large dense core vesicles and small clear vesicles) one. The reaction products were also found in the extracellular spaces surrounding the axons. Sometimes the reaction products were seen in the coated pits or the endocytotic vesicles of the odontoblast processes. The present study demonstrated that nerve endings (varicosities) derived from the trigeminal ganglion were present in the dentinal tubules, and that WGA-HRP extracellularly extruded from the sensory nerves in the odontoblastic layer or predentin/dentin. These findings thus suggest that sensory nerves may have some (e.g., trophic) effect on either odontoblasts or the environment around the sensory nerves in the dentin/pulp.     

Significance of cardiac innervation on spontaneous ventricular arrhythmias elicited by left stellate ganglion stimulation in dogs 4 days after myocardial infarction: comparison of two experimental models

The effects of cardiac sympathetic overactivity on spontaneous arrhythmias and transmural left ventricular effective refractory period (LVERP) were assessed by left stellate stimulation (LSS) in 16 anesthetized dogs. The experiments were performed 4 days after proximal occlusion of the left anterior descending (LAD) coronary artery produced by either ligation (9 dogs) or embolization with histoacryl (7 dogs). The innervation of left ventricular myocardium was studied by light and electron microscopies. Synaptophysin (SYN)- and neuropeptide Y (NPY)-immunoreactive nerve fibers and terminals were thereby detected. In dogs subjected to ligation, LSS elicited negligible arrhythmias in spite of a decrease in LVERP by 6.9 +/- 2.2% (mean +/- SD, p < 0.001). However, dogs with intravascular occlusion were more susceptible to LSS, as indicated by development of sustained ventricular rhythms. In these animals, the LVERP decreased with LSS by 14.6 +/- 3.4% (p < 0.001). The innervation of the anterior left ventricular wall distal to the place of occlusion revealed a higher reduction of SYN- and NPY-immunoreactive nerves in infarcted myocardium and a more heterogeneous distribution of nerves in undamaged regions after ligation, compared to intravascular occlusion. Ultrastructurally, nerve terminals containing small agranular and large dense-core vesicles were found innervating ischemically damaged myocardiocytes. Our findings indicate a higher preservation of nerves in infarcted and noninfarcted myocardium of animals subjected to embolic occlusion of the LAD. Because LSS apparently elicited more arrhythmias in these animals, we suggested a proarrhythmic effect of intact myocardial innervation after infarction.     

Endothelin ET(B) receptor-mediated constriction in the rabbit basilar artery

The present study tests whether endothelin ET(B) receptor activation can mediate endothelin-1 constriction in the rabbit basilar artery in situ. Endothelin-1 (30 nM) induced 27% constriction of vessels pretreated with 1 microM BQ610 (homopiperidenyl-CO-Leu-DTrp (CHO)-D-Trp-OH), an endothelin ET(A) receptor antagonist, and the resulting constriction was completely relaxed by BQ788 (N-cis-2,6-dimethylpiperidinocarbonyl L-gamma-MeLeu-D-Trp (COOCH3)-Nle), an endothelin ET(B) receptor antagonist. Similarly, 30 nM endothelin-1 induced 30% constriction of vessels pretreated with 1 microM BQ788, and the resulting constriction was completely relaxed by BQ610. In contrast, sarafotoxin S6c, an endothelin ET(B) receptor agonist, did not induce constriction. This study suggests that in the basilar artery (1) endothelin ET(B) receptor activation can result in constriction and (2) the ability to elicit constriction is in some way dependent upon the agonist that activates the endothelin ET(B) receptor.     

ATP-sensitive potassium channels in the basilar artery during chronic hypertension

We examined the hypothesis that dilatation of the basilar artery in response to activation of ATP-sensitive potassium channels is impaired in stroke-prone spontaneously hypertensive rats (SHRSP). Changes in basilar artery diameter in response to aprikalim, a direct activator of ATP-sensitive potassium channels, were measured in anesthetized SHRSP and normotensive Wistar-Kyoto (WKY) rats through a cranial window. Topical application of aprikalim increased basilar artery diameter in WKY rats. Glibenclamide, a selective inhibitor of ATP-sensitive potassium channels, abolished aprikalim-induced vasodilatation. Thus, ATP-sensitive potassium channels are functional in the basilar artery of WKY rats in vivo. Aprikalim (10(-6) mol/L) dilated the basilar artery by 31 +/- 5% (mean +/- SEM) in WKY rats but only 5 +/- 1% in SHRSP. The concentration-response curve to aprikalim in SHRSP was significantly shifted to the right, but the response to the highest concentration of aprikalim (10(-5.5) mol/L) was similar in SHRSP and WKY rats. Vasodilatation in response to norepinephrine was also impaired in SHRSP. Dilator responses of the basilar artery to forskolin, a direct activator of adenylate cyclase, and nitroprusside, a direct activator of guanylate cyclase, were normal in SHRSP. The findings suggest that dilatation of the basilar artery in response to direct activation of ATP-sensitive potassium channels is impaired in SHRSP compared with WKY rats in vivo.     

Comparison of spontaneously released endothelium-derived relaxing factor in cerebral and extracerebral arteries in rabbits

To investigate regional differences in spontaneously released endothelium-derived relaxing factor (EDRF), a bioassay of spontaneously released EDRF was performed on rabbit basilar, ear, common carotid and thoracic arteries using an isometric tension measurement technique and a measurement of cyclic guanosine monophosphate (cGMP) content in the vascular smooth muscle. The amount of spontaneously released EDRF was higher in the basilar artery than in any other arteries examined (p < 0.01). The levels of cGMP were 57.3 +/- 4.4 (n = 7) in basilar, 26.5 +/- 4.3 (n = 6) in ear, 24.5 +/- 2.3 (n = 11) in common carotid, and 30.3 +/- 3.8 pmol/g tissue (n = 8) in thoracic artery with endothelium, while endothelium-denuded arteries showed 24.2 +/- 6.6 (n = 5), 17.5 +/- 5.1 (n = 6), 20.1 +/- 2.9 (n = 7) and 14.4 +/- 2.3 pmol/g tissue (n = 8) in the same order. Haemoglobin (10(-5) M, incubated with the artery for 5 min, significantly reduced the level of cGMP in all vessels with endothelium: 35.3 +/- 4.4 (basilar), 16.0 +/- 2.1 (ear), 14.0 +/- 1.9 (common carotid) and 8.7 +/- 1.2 pmol/g tissue (thoracic artery). Since endothelium-dependent relaxation is associated with a rise in the cGMP content of the smooth muscle cell, the data of cGMP measurement in addition to the bioassay of spontaneously released EDRF in tension measurement suggests that the spontaneous release of EDRF is much greater in the basilar artery than in extracerebral arteries. It is concluded that the intensity of the spontaneously released EDRF is relatively higher in the intracerebral artery than in the extracerebral artery.     

Intramembrane structure of the sensory axon terminals in bullfrog muscle spindles

Much physiologic and morphologic research has been done into the sensory mechanism of the frog muscle spindle. However, no freeze-fracture study has described in detail the shape and intramembrane structure of the nonmyelinated sensory axon terminals of the frog muscle spindle. In this study, muscle spindles were isolated from the red part of bullfrog semitendinous muscles. Chemically fixed spindles were subjected to freeze fracturing. The sensory axon endings were reconstructed, and the size and density of intramembrane particles (IMPs) were measured along the sensory nerve endings. The axon terminals had four distinctive parts: parent trunks (>0.5 microm in diameter), primary branches (0.15-0.5 microm), terminal branches (<0.1 pm), and varicosities (0.02-0.5 microm). IMPs ranged from 5 nm to 21 nm in diameter and were present in the intramembrane space of the plasma membrane all throughout the nonmyelinated sensory nerve endings. Mean IMP sizes in the protoplasmic face (PF) and the external face (EF), respectively, were 8.1 nm and 8.4 nm in the parent trunks, 8.8 nm and 8.8 nm in the primary branches, 9.4 nm and 9.0 nm in the varicosities, and 8.7 nm and 8.7 nm in the terminal branches. Mean IMP size in the PF was smallest in the parent trunk and largest in the varicosity. Mean IMP densities (numbers of IMPs per microm2) in the PF and the EF, respectively, were 2,500 and 700 in the parent trunks, 2,200 and 500 in the primary branches, 1,700 and 400 in the varicosities, and 1,000 and 300 in the terminal branches. Density decreased with the tapering of the axon terminal, with IMPs distributed evenly in the PF and the EF. The characteristic intramembrane structure of sensory nerve endings is discussed.     

Localization of substance P and leucine enkephalin in the nerve terminals of the guinea pig paracervical ganglion

Immunoreactivities (IR) of substance P and leucine enkephalin have been demonstrated in the guinea-pig paracervical ganglion by an immunogold electron microscope method. Both substance P-IR and leucine enkephalin-IR were detected in large synaptic vesicles with electron-dense cores. The former neuropeptide was detected in nerve terminals and varicosities comprised mainly of large vesicles with electron-dense cores; the latter was detected in nerve terminals and varicosities that also included small, clear synaptic vesicles. In a minority of nerve terminals and varicosities coexistence of both immunoreactivities could be demonstrated within vesicles with an electron-dense core. Also present in these nerve terminals and varicosities were small, clear synaptic vesicles, though these were unreactive.     

Specificity and sensitivity of distinctive chest radiographic and/or 67Ga images in the noninvasive diagnosis of sarcoidosis

1. Experimental chronic cerebral vasospasm induced by subarachnoid haemorrhage (SAH) in rabbits was studied in order to evaluate the efficacy of repeated i.v. infusion of Iloprost (ILO). 2. The mean diameter of the basilar artery of intact animals was calculated as 737.5 +/- 52.8 microns while this value was reduced to 237.5 +/- 22.96 microns after SAH. 3. In the ILO treated group the mean diameter of the basilar artery was significantly increased and found to be 593.75 +/- 64.0 microns. 4. No change was observed in intracranial pressure (ICP) except a slight decrease in mean arterial pressure when relatively higher doses of ILO were used. 5. These results were taken as evidence of the high therapeutic value and low side effects of ILO in the treatment of persisting cerebral vasospasm due to SAH.     

Light and electron microscopic localization of acetylcholinesterase activity in the rat renal nerves

Acetylcholinesterase activity is shown in the renal nerves of the rat with the technique of Karnovsky and Roots. By light microscopy, the acetylcholinesterase-positive nerves are seen in association with blood vessels, including the glomerular arterioles, and occasionally with renal tubules. By electron microscopy the precipitate appears extracellularly around axons and varicosities. DFP inhibits the deposition of precipitate. Previous demonstration by serial section electron microscopy in the rat revealed that all nerves around the glomerular arterioles contain small dense-cored vesicles characteristic of adrenergic nerves, indicating that the acetylcholinesterase-positive nerves demonstrated here are likely to be adrenergic nerves containing acetylcholinesterase.     

Protein synthesis and immunoreactivities of contraction-related proteins in smooth muscle cells of canine basilar artery after experimental subarachnoid hemorrhage

We examined time-dependent changes in protein synthesis and in the immunoreactivities of representative contraction-related structural proteins in smooth muscle cells of canine basilar arteries after experimental subarachnoid hemorrhage (SAH). Protein synthesis was assessed by the percentage of polyribosome-forming ribosomes to total ribosomes (aggregation rate), a morphological index of the activity of protein synthesis. The aggregation rates in prostaglandin F2 alpha-(PGF 2 alpha) and 12-O-tetradecanoyl-phorbol-13-acetate (TPA)-induced contracted basilar arteries were 70.0 +/- 7.0% and 71.4 +/- 8.7%, respectively, quite similar to the value in normal basilar artery (73.0 +/- 8.0%). In the single-SAH group with little delayed histological changes in the basilar arteries, the aggregation rate was significantly decreased to 30.5 +/- 6.4% by 24 h after the SAH, and recovered to 52.3 +/- 9.0% and 70.2 +/- 7.6% at 7 and 14 days postSAH, respectively, when the vasospasm was moderately and completely ameliorated. In contrast, in the double-SAH group in which the basilar arteries developed delayed smooth muscle cell death and long-lasting arterial contraction, a significant decrease in the aggregation rate (25.0 +/- 5.0% on day 4) persisted for 14 days. The in vitro incorporation of [3H]-leucine in the basilar arterial cells was also significantly suppressed 4 and 7 days after the initial SAH (1.2 +/- 0.4 and 1.4 +/- 0.3 x 10(3) dpm/mg protein) in the double-SAH group, as opposed to no significant decrease in the basilar artery at 7 days postSAH in the single-SAH group (1.9 +/- 0.6 x 10(3) dpm/mg protein). The immunoreactivity of alpha-smooth muscle actin, a contractile protein, demonstrated by immunohistochemistry and immunoblots, was not altered for up to 14 days even in the double-SAH group, but that of calponin and of h-caldesmon, contraction-inhibiting proteins, was markedly reduced 4-14 days after the initial SAH. Persistent impairment of protein synthesis and relative reduction of immunoreactivities of the contraction-inhibiting proteins were observed in arteries with severe vasospasm and loss of smooth muscle cells, as noted in the double-SAH subjects. These abnormalities may cooperate to cause cerebral arterial narrowing accompanied by degeneration of smooth muscle cells after SAH.     

Three-vessel study of cerebral blood flow using phase-contrast magnetic resonance imaging: effect of physical characteristics

The development of phase-contrast magnetic resonance imaging (P-C MRI) provides a noninvasive method for measurement of volumetric blood flow (VFR). We performed P-C MRI to study the effects of physical characteristics on cerebral blood flow. VFR of the left and right internal carotid arteries and basilar artery were measured using P-C MRI and total cerebral blood flow (tCBF) was calculated by summing up the VFR values in the three vessels. Moreover, we investigated the changes in these blood flows as influenced by age, head size, height, weight, body surface area, and handedness. The blood flows were 142 +/- 58 ml/min (mean +/- standard deviation) in the basilar artery; and 229 +/- 86 ml/min in the left, and 223 +/- 58 ml/min in the right internal carotid artery; and tCBF was 617 +/- 128 ml/min. Significant increases were observed in head size-related change of VFR in the basilar artery (p = .028) and height-related change of tCBF (p = .045). The other characteristics did not significantly influence any VFR. The results suggest that head size and height may reflect CBF, and that these effects should be considered when changes of CBF are diagnosed. Phase-contrast MRI is useful for a noninvasive and rapid analysis of cerebral VFR and has potential for clinical use.     

Possibilities for a cholinergic action on smooth musculature and on sympathetic axons in brain vessels mediated by muscarinic and nicotinic receptors

A pharmacological identification and characterization of cholinergic receptors was carried out in pial arteries of cats. In one series of experiments, the middle cerebral artery was suspended in an organ bath for recording fo circular motor activity. Parasympathomimetic compounds produced either a relaxation or a contraction. The relaxation occurred at low doses (up to 10(-6) M), and the response was inhibited in a competitive manner by atropine. The mean KB value (determined with acetylcholine as agonist) was 3.85 X 10(-11) M, and the corresponding pA2 value 10.43. At higher doses, the parasympathomimetics produced a contraction. This effect, too, was inhibited in a competitive manner with atropine. The calculated mean KB value with acetylcholine as agonist was 1.12 X 10(-11) M, and pA2 was 10.07. The motor responses did not require an intact perivascular sympathetic innervation, which shows that the effects were mediated by muscarinic type of cholinergic receptors present in the smooth musculature. In another series of experiments, pial arteries were preincubated in the presence of 3H-norepinephrine, and the amount of tritium efflux was measured in a superfusion system before or during electrical field stimulation (12 V, 1 msec pulse duration, 10 Hz). The efflux was minimized by sympathetic denervation, and the effect of transmural stimulation abolished by bretylium and guanethidine, which shows that the bulk of tritium overflow during stimulation originated from the perivascular sympathetic nerves. The marked elevation of tritium efflux during stimulation was enhanced by hexamethonium, and it was inhibited by nicotine and acetylcholine, whose effects were counteracted by hexamethonium (but not by atropine). This finding indicates the presence of nicotinic type of cholinergic receptors on the perivascular adrenergic nerves, allowing inhibition of norepinephrine by acetylcholine that may be liberated from the adjacent cholinergic terminals in the autonomic nerve plexus.     

Electron cryomicroscopy of bacteriorhodopsin vesicles: mechanism of vesicle formation

We obtained vesicles from purple membrane of Halobacterium halobium at different suspension compositions (pH, electrolytes, buffers), following the procedure of Kouyama et al. (1994) (J. Mol. Biol. 236:990-994). The vesicles contained bacteriorhodopsin (bR) and halolipid, and spontaneously formed during incubation of purple membrane suspension in the presence of detergent octylthioglucoside (OTG) if the protein:OTG ratio was 2:1 by weight. The size distribution of the vesicles was precisely determined by electron cryomicroscopy and was found to be almost independent on the incubation conditions (mean radius 17.9-19 nm). The size distribution in a given sample was close to the normal one, with a standard deviation of approximately +/- 1 nm. During dialysis for removal of the detergent, the vesicles diminished their radius by 2-2.5 nm. The results allow us to conclude that the driving force for the formation of bR vesicles is the preferential incorporation of OTG molecules in the cytoplasmic side of the membrane (with possible preferential delipidation of the extracellular side), which creates spontaneous curvature of the purple membrane. From the size distribution of the vesicles, we calculated the elasticity bending constant, K(B) approximately 9 x 10(-20) J, of the vesicle wall. The results provide some insight into the possible formation mechanisms of spherical assembles in living organisms. The conditions for vesicle formation and the mechanical properties of the vesicles could also be of interest with respect to the potential technological application of the bR vesicles as light energy converters.     

Vasodilator effects on canine basilar artery induced by intracisternal interleukin-1 beta

The effect of interleukin-1 beta (IL-1 beta) on a cerebral artery was investigated in anesthetized dogs. Intracisternal administration of IL-1 beta (0.03 and 0.3 micrograms) dilated the canine basilar artery in a dose-dependent manner, without affecting systemic blood pressure or heart rate. The increase in diameter induced by 0.3 micrograms of IL-1 beta was 28.4% +/- 13.4% of control at 2 hours and was inhibited by 30 micrograms of the IL-1 beta receptor antagonist, zinc protoporphyrin (4.5% +/- 13.5%, P < 0.05). Interleukin-1 beta did not affect the concentration of nitric oxide metabolites in CSF. However, there was an increase in the concentration of eicosanoids in CSF, and the elevation of 6-keto-PGF1 alpha paralleled the vasodilation. Pretreatment with 30 micrograms of the selective inducible cyclooxygenase (COX-2) inhibitor NS-398 also inhibited the IL-1 beta-induced vasodilation significantly (5.9% +/- 9.4% at 2 hours, P < 0.01). Western blot analysis revealed the expression of a 68-kD COX-2-like protein in basilar artery extracts. These findings suggest that the IL-1 beta-induced vasodilator effect is linked to the prostaglandin cascade, predominantly to prostaglandin I2, by induction of COX-2, but not to the stimulation of nitric oxide metabolism.     

Role of endothelin receptors, calcium and nitric oxide in the potentiation by endothelin-1 of the sympathetic contraction of rabbit ear artery during cooling

1. To examine further the potentiation by endothelin-1 on the vascular response to sympathetic stimulation, we studied the isometric response of isolated segments, 2 mm long, from the rabbit central ear artery to electrical field stimulation (1-8 Hz), under different conditions, at 37 degrees C and during cooling (30 degrees C). 2. Electrical stimulation produced frequency-dependent contraction, which was reduced (about 63% for 8 Hz) during cooling. At 30 degrees C, but not at 37 degrees C, endothelin-1 (1, 3 and 10 nM) potentiated the contraction to electrical stimulation in a dose-dependent way (from 43 +/- 7% to 190 +/- 25% for 8 Hz). 3. This potentiation by endothelin-1 was reduced by the antagonist for endothelin ETA receptors BQ-123 (10 microM) but not by the antagonist for endothelin ETB receptors BQ-788 (10 microM). The agonist for endothelin ETB receptors IRL-1620 (0.1 microM) did not modify the contraction to electrical stimulation. 4. The blocker of L-type Ca2+ channels verapamil (10 microM l-1) reduced (about 72% for 8 Hz) and the unspecific blocker of Ca(2+)-channels NiCl2 (1 mM) practically abolished (about 98%), the potentiating effects of endothelin-1 found at 30 degrees C. 5. Inhibition of nitric oxide synthesis with NG-nitro-L-arginine (L-NOARG, 0.1 mM) increased the contraction to electrical stimulation at 30 degrees C more than at 37 degrees C (for 8 Hz, this increment was 297 +/- 118% at 30 degrees C, and 66 +/- 15% at 37 degrees C). Endothelium removal increased the contraction to electrical stimulation at 30 degrees C (about 91% for 8 Hz) but not at 37 degrees C. Both L-NOARG and endothelium removal abolished the potentiating effects of endothelin-1 on the response to electrical stimulation found at 30 degrees C. 6. These results in the rabbit ear artery suggest that during cooling, endothelin-1 potentiates the contraction to sympathetic stimulation, which could be mediated at least in part by increasing Ca2+ entry after activation of endothelin ETA receptors. This potentiating effect of endothelin-1 may require the presence of an inhibitory tone due to endothelial nitric oxide.     

Structure of a juxtaglomerular cell tumor: the presence of a neural component: a light and electron microscopic study

A 15-year-old girl with hypertension, markedly elevated plasma renin activity, and normal aortogram had a well encapsulated tumor nodule removed from the right kidney. Following surgery, the plasma renin activity and blood pressure became normal and have remained so for the past 12 months. The tumor consisted of juxtaglomerular cells filling the interstitium between endothelium-lined vascular spaces. Electron microscopy disclosed the presence in the interior of the tumor, of unmyelinated nerve bundles with varicosities containing the small, densely cored vesicles characteristic of adrenergic nerves. Nerve terminals were in contact with the juxtaglomerular tumor cells. No basement membrane material was interposed between the nerve endings and the tumor cell; the width of the gap between the two plasma membranes was approximately 150 A. The presence of sympathetic fibers in the juxtaglomerular cell tumor underscores the close biologic relationship between the sympathetic and renin systems.