Intrastriatal transplantation of Sertoli cells may improve amphetamine-induced rotation and tyrosine hydroxylase immunoreactivity of the striatum in hemiparkinsonian rats

This study investigated survival and neurotrophic effects of Sertoli cells transplanted in the striatum of 6-hydroxydopamine (6-OHDA)-induced hemiparkinsonian rats. Primary cultures of Sertoli cells were established from 3-week old rats and characterized by associated marker, placental cadherin (P-cadherin). Two months after transplantation, amphetamine-induced rotations of rats transplanted with Sertoli cells were significantly lower than those of control rats. However, restoration of tyrosine hydroxylase (TH) immunoreactivity and Sertoli cells that expressed P-cadherin were only found in the striatum of the rat that showed full recovery from amphetamine-induced rotation 3 months after transplantation without immunosuppression. These results suggest that Sertoli cells transplanted in striatum of hemiparkinsonian rats may survive for at least 3 months, and improve amphetamine-induced rotation and restore TH immunoreactivity.

Carboxyfullerene prevents iron-induced oxidative stress in rat brain

Carboxyfullerene, a water-soluble carboxylic acid derivative of a fullerene, was investigated as a protective agent against iron-induced oxidative stress in the nigrostriatal dopaminergic system of anesthetized rats. Intranigral infusion of exclusive carboxyfullerene did not increase lipid peroxidation in substantia nigra or deplete dopamine content in striatum. Infusion of ferrous citrate (iron II) induced degeneration of the nigrostriatal dopaminergic system. An increase in lipid peroxidation in substantia nigra as well as decreases in K+-evoked dopamine overflow and dopamine content in striatum were observed 7 days after the infusion. Co-infusion of carboxyfullerene prevented iron-induced oxidative injury. Furthermore, tyrosine hydroxylase-immunoreactive staining showed that carboxyfullerene inhibited the iron-induced loss of the dopaminergic nerve terminals in striatum. The antioxidative action of carboxyfullerene was verified by in vitro studies. Incubation of brain homogenates increased the formation of the Schiff base fluorescent products of malonaldehyde, an indicator of lipid peroxidation. Both autooxidation (without exogenous iron) and iron-induced elevation of lipid peroxidation of brain homogenates were suppressed by carboxyfullerene in a dose-dependent manner. Our results suggest that intranigral infusion of carboxyfullerene appears to be nontoxic to the nigrostriatal dopaminergic system. Furthermore, the potent antioxidative action of carboxyfullerene protects the nigrostriatal dopaminergic system from iron-induced oxidative injury.

Neuronal supernumerary and dendritic sprouting of the nucleus ambiguus after chronic alteration of peripheral targets in cats

Anatomic changes of neuronal profiles in response to chronic alteration of peripheral targets were investigated in the nucleus ambiguus (NA) of cats. Unilateral vagal-hypoglossal nerve anastomosis was performed by suturing the transected proximal stump of the vagus nerve to the transected distal stump of the hypoglossal nerve. After comparing horseradish peroxidase (HRP)-labeled neurons on the ipsilateral operated side of the NA with the contralateral unoperated NA and the NA following transection and reuniting to the vagus itself, a remarkable ramification and elongation of the dendritic trees was observed in the HRP-positive neurons on the ipsilateral NA. Quantitative analysis of neuronal profiles revealed that the number of the medium and large neurons on the ipsilateral NA was greater than the contralateral NA and the NA following autologous suturing of the vagus. Comparisons of variable dendritic lengths of the medium and large neurons on the ipsilateral NA revealed longer distances and more branches of the tertiary and perisomatic dendrites than those of the contralateral NA and the NA ipsilateral to autologous reunion. Our results suggest that remarkable sprouting and elongation of the dendritic trees as well as cell supernumerary occurred in the dominant NA motoneurons ipsilateral to the nerve anastomosis. In conclusion, there is a trophic influence in the tongue musculature, which was retrogradely transported to the NA neurons via the regenerating axons and caused the morphological changes in the NA in response to the rerouting of efferents from the vagus nerve to the hypoglossal nerve to innervate intimate tongue musculature.

Immunohistochemical evidence of down-regulation of mu-opioid receptor after chronic PL-017 in rats

In a previous study, mu-opioid receptor binding was decreased by chronic treatment of rats with a mu-opioid receptor-selective agonist [CH3Phe3, D-Pro4]morphiceptin (PL-017) [Tao, P.L., Lee, H.Y., Chang, L.R., Loh, H.H., 1990. Decrease in mu-opioid receptor binding capacity in rat brain after chronic PL-017 treatment. Brain Res. 526, 270-275]. However, there was a lack of correlation between the time course of receptor down-regulation and the loss of pharmacological effects of the drug. In the current study, we used immunohistochemistry to reinvestigate this issue. Male Sprague-Dawley rats were chronically treated with PL-017 i.c.v. for 1, 3 or 5 days, using an escalating dosage paradigm (0.75-6.0 microg), which resulted in a 1.4 to 32-fold increase in the AD50. Rat brains were removed, frozen, coronally sectioned (14 microm) and processed for mu-, delta- or kappa-opioid receptor immunohistochemistry by the avidin-biotin complex (ABC) method. Significant decreases in OP3 immunodensity were found in many brain regions which are enriched with OP3 after chronic treatment of PL-017. Time-dependent decreases in OP3 were detected and reached a plateau around 3 days of PL-017 treatment. No significant change in OP1 or OP2 immunodensity after chronic treatment with PL-017 was found. Our conclusion is that chronic treatment with PL-017 of rats selectively down-regulates mu-opioid receptors in the brain. This may be an important mechanism for PL-017 tolerance.

Fumonisins as a possible contributory risk factor for primary liver cancer: a 3-year study of corn harvested in Haimen, China, by HPLC and ELISA

Employing HPLC fluorometry, gas-liquid chromatography (GLC) and a novel enzyme-linked immunosorbent assay (ELISA) based on a monoclonal antibody, 40 corn samples, each collected in 1993 from agricultural stocks for human consumption in Haimen (Jiangsu County) and Penlai (Shandong Province), high- and low-risk areas for primary liver cancer (PLC) in China, respectively, were analysed for fumonisins (FBs), aflatoxins (AFs) and trichothecenes. Levels and positive rates of FBs and deoxynivalenol (DON) were significantly higher in Haimen than in Penlai. ELISA of the 40 corn samples harvested in the two areas in 1994 revealed that FB contamination levels and rates in these areas were comparable to those observed in 1993 in Haimen. ELISA analysis of 1993 and 1994 products revealed a wide occurrence of AFB1 but the positive rates as well as levels were not significantly different between these areas. ELISA of the same sample number of corn harvested in 1995 revealed that FB contamination in Haimen was significantly higher than in Penlai. These 3-yearly surveys of corn samples (240 in total) demonstrated that corn harvested in Haimen was highly contaminated with FBs and that the contamination level, as well as positive rate in 1993 and 1995, were 10-50-fold higher than those in Penlai, suggesting FBs as a risk factor for promotion of PLC in endemic areas, along with the trichothecene DON. Co-contamination with AFs, potent hepatocarcinogens, was assumed to play an important role in the initiation of hepatocarcinogenesis.

Transplantation of microencapsulated PC12 cells provides long-term improvement of dopaminergic functions

The purpose of this study is to examine if microencapsulated PC12 cells may provide long term effects to the hemiparkinsonian rats. A modified technique was used to encapsulate PC12 cells into gelled microspheres. We found that the PC12 cells can survive in the modified microcapsules in vitro. Most of the PC12 cells formed cluster 3 weeks after incubation. The PC12 cell-loaded microcapsules were also examined in vitro. Adult Sprague-Dawley rats, anesthetized with chloral hydrate, were injected unilaterally with 6-hydroxydopamine into the medial forebrain bundle. The effectiveness of this lesion was tested by measuring apomorphine or methamphetamine-induced rotation one month after lesioning. The unilaterally lesioned rats were transplanted with microencapsulated PC12 cells. Results showed that apomorphine and methamphetamine-induced rotations were greatly suppressed after transplantation. One year after the grafting, the animals were anesthetized with urethane for the voltammetric study. Low dose of KCl was directly injected into the grafted striatum through pressure microejection. We found that KCl-induced DA release, as measured by voltammetric techniques, was regenerated in the striatum. The animals were later sacrificed for histological examination. We found that capsules were present in the lesioned striatum one year after grafting. Most of the capsules contained no PC12 cell. However, some capsules were filled entirely with PC12 cells. Taken together, our data suggested that PC12 cells can survive in the capsule in vitro and may provide long-term dopaminergic effects to the hemiparkinsonian rats.

Importance of a conserved phenylalanine-35 of cytochrome b5 to the protein's stability and redox potential

Phenylalanine-35, which is a residue of the hydrophobic patch on the surface of cytochrome b5, has been mutated into Tyr35, His35 and Leu35 to elucidate the functions of the Phe35 and give further insight into the roles of the hydrophobic patch and/or aromatic network. The effects of these mutations on the heme environment, denaturation towards heating and the denaturant urea, redox potential and stability of protein were studied. The relative stability of cytochrome b5 and its mutants towards heating has the order Phe35Tyr > wild type > Phe35Leu > Phe35His in the oxidized state and wild type > Phe35Tyr > Phe35Leu > Phe35His in the reduced state. All the mutants exhibit decreased reduction potentials: Phe35Tyr -66 mV, Phe35His -51 mV and Phe35Leu -28 mV, which are more negative than that of the wild type. The order of redox potential reflects the relative stability in the oxidized and reduced states. A method of producing multiple mutants at a single site of a gene is also described for the first time.

k-winners-take-all neural net with Theta(1) time complexity

In this article we present a k-winners-take-all (k-WTA) neural net that is established based on the concept of the constant time sorting machine by Hsu and Wang. It fits some specific applications, such as real-time processing, since its Theta(1) time complexity is independent to the problem size. The proposed k-WTA neural net produces the solution in constant time while the Hopfield network requires a relatively long transient to converge to the solution from some initial states.

Restoration of dopamine overflow and clearance from the 6-hydroxydopamine lesioned rat striatum reinnervated by fetal mesencephalic grafts

The purpose of these experiments was to investigate the electrochemical indices of mesencephalic dopaminergic grafts as they function in the rat striatum. Sprague-Dawley rats were injected unilaterally with 6-hydroxydopamine into the medial forebrain bundle, and the effectiveness of these lesions was tested by measuring apomorphine-induced rotation. The unilaterally lesioned rats were later transplanted with fetal ventral mesencephalon. Only animals receiving ventral mesencephalon transplants showed significant decreases in rotation after grafting. High-speed chronoamperometric recording techniques using Nation-coated carbon fiber electrodes were used to evaluate dopamine (DA) overflow in the striatum of urethane-anesthetized rats. We found that 6-hydroxydopamine lesions resulted in a loss of KCl-induced DA overflow and clearance. Ventral mesencephalon grafts restored neurochemical indices. The zone of normalized DA clearance was considerably larger than that of normalized release. Furthermore, histochemical studies using tyrosine hydroxylase immunoreactivity confirmed graft survival and neurite outgrowth from the graft into the lesioned striatum. In conclusion, these findings suggest that the behavioral improvements by grafts of fetal mesencephalic tissue are accompanied by morphological and electrochemical evidence of reinnervation and the restoration of DA input. Measurement of DA clearance may reveal a wider area of reinnervation than that indicated by more traditional immunocytochemical methods.

Experimental study on the occlusion of arterial blood flow by the implantation of nitinol alloy stents

To evaluate the occlusion of arteries, 6 conic intravascular endoprosthetic stents of titanium-nickel alloy were implanted transluminally to the right external iliac arteries in 2 normal dogs and 4 normal pigs. The stent was characterized by ductility below 313 K (40 degrees C) and restoration memory-shape between 313-319 K. The diameter of the large end of conic stent was 4.0 mm (dog) and 4.5 mm(pig). The topographic anatomy showed that the external iliac artery was near complete occlusion, with a very small residual lumen (about 1 mm in diameter) in dogs at 6 months, with complete occlusion in pigs at 8 months. The histopathological examination indicated that the arterial intima of the upper branch from the stented site was smooth, and that neither inflammatory cell infiltration nor foreign giant cell reaction was found. The newly formed granulation tissue inside the stent came from emboli organization. These results suggest that the shape-memory alloy stent has good biocompatibility and the conic intravascular endoprosthetic stent might completely occlude arterial blood flow.

Sepsis-induced apoptosis of the thymocytes in mice

Intraperitoneal injection of Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa) induces thymic atrophy in mice. The thymus weight, cell number, and viability began to decrease at 3 h, and reached their lowest level at 72 h. The thymocyte death was associated with DNA fragmentation of approximately 200 base pairs in ladder form. The kinetic study on histopathology revealed the process of thymocyte death and thymic atrophy. Flow-cytometric analysis showed that CD4+CD8+ thymocytes decreased predominantly. LPS caused thymocyte apoptosis, but only in LPS-responder mice, unlike Gram-negative bacteria that induced apoptosis in both LPS-responder (C3H/HeN) and LPS-nonresponder (C3H/HeJ). Gram-positive bacteria Streptococcus pneumoniae also caused apoptosis in LPS-nonresponder (C3H/HeJ) and LPS-responder mice (B6). The kinetics of serum TNF-alpha production after Gram-negative or Gram-positive bacteria injection was slightly different. E. coli induced serum TNF-alpha peak at 1 h in B6 mice, whereas S. pneumoniae induced a peak at 6 h in C3H/HeJ and at 9 h in B6 mice. Similarly, S. pneumoniae induced thymocyte apoptosis around 9 to 12 h, which was 6 to 9 h later than that observed with E. coli in B6 mice. Anti-TNF-alpha Ab completely blocked the E. coli-induced thymocyte apoptosis, but was only partially inhibitory on the S. pneumoniae-induced thymocyte apoptosis. Furthermore, thymocyte apoptosis induced by E. coli was inhibited by cycloheximide or actinomycin D. These data indicate that both Gram-negative and Gram-positive bacteria could induce thymus atrophy via apoptosis, and that TNF-alpha is a common denominator released and might be responsible for the thymocyte apoptosis.

Sepsis-induced apoptosis of the thymocytes in mice

Intraperitoneal injection of Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa) induces thymic atrophy in mice. The thymus weight, cell number, and viability began to decrease at 3 h, and reached their lowest level at 72 h. The thymocyte death was associated with DNA fragmentation of approximately 200 base pairs in ladder form. The kinetic study on histopathology revealed the process of thymocyte death and thymic atrophy. Flow-cytometric analysis showed that CD4+CD8+ thymocytes decreased predominantly. LPS caused thymocyte apoptosis, but only in LPS-responder mice, unlike Gram-negative bacteria that induced apoptosis in both LPS-responder (C3H/HeN) and LPS-nonresponder (C3H/HeJ). Gram-positive bacteria Streptococcus pneumoniae also caused apoptosis in LPS-nonresponder (C3H/HeJ) and LPS-responder mice (B6). The kinetics of serum TNF-alpha production after Gram-negative or Gram-positive bacteria injection was slightly different. E. coli induced serum TNF-alpha peak at 1 h in B6 mice, whereas S. pneumoniae induced a peak at 6 h in C3H/HeJ and at 9 h in B6 mice. Similarly, S. pneumoniae induced thymocyte apoptosis around 9 to 12 h, which was 6 to 9 h later than that observed with E. coli in B6 mice. Anti-TNF-alpha Ab completely blocked the E. coli-induced thymocyte apoptosis, but was only partially inhibitory on the S. pneumoniae-induced thymocyte apoptosis. Furthermore, thymocyte apoptosis induced by E. coli was inhibited by cycloheximide or actinomycin D. These data indicate that both Gram-negative and Gram-positive bacteria could induce thymus atrophy via apoptosis, and that TNF-alpha is a common denominator released and might be responsible for the thymocyte apoptosis.

Precollicular decerebration reduces the pressor responses evoked by stimulation of rostral pons but not medulla in cats

In 30 cats under chloralose (40 mg/kg) and urethane (400 mg/kg) anesthesia, the ponto-medullary region involved in cardiovascular integration were stimulated by rectangular pulses (0.5 ms, 80 or 5 Hz, 100 to 200 microA) and/or by microinjection of sodium glutamate (Glu, 0.25-0.5 M, 70-200 nl). Changes of systemic arterial blood pressure (SAP) and renal sympathetic nerve activity (RNA) following stimulation were compared before and after precollicular decerebration. Precollicular decerebration itself resulted in an immediate but brief (5 to 15 min) hypotension with a decrease in SAP ranging from 40 to 100 mmHg. Stimulation of the lateral tegmental field (FTL) produced depressor responses. After precollicular decerebration, the stimulation induced depressor responses were either abolished or converted to mild pressor responses. Stimulation of the dorsal gigantocellular tegmental field-periventricular grey (dFTG-PVG) produced pressor responses. These responses were abolished after precollicular decerebration without exception. On the other hand, precollicular decerebration did not reduce pressor responses produced by stimulation of the ventrolateral medulla (VLM) and the dorsal medulla (DM). In 7 additional cats killed with an overdose of pentobarbital, the brain stem were processed for dopamine beta-hydroxylase (DBH). The pressor areas of the VLM and DM were DBH positive, indicating the presence of norepinephrine, while the dFTG-PVG and FTL were not. These findings suggest that the depressor mechanism of the FTL and the pressor mechanism of the dFTG, but not of the VLM or DM depend on actions of the brain structures rostral to superior colliculi.

Activation of neurons in cardiovascular areas of cat brain stem affects spinal reflexes

In 65 cats anesthetized with chloralose (40 mg/kg) and urethane (400 mg/kg), the effects of electrical stimulation and microinjection of sodium glutamate (0.25 M, 100-200 nl) in the pressor areas in the rostral brain stem on the evoked L5 ventral root response (EVRR) due to intermittent stimulation of sciatic afferents were compared to stimulating the dorsomedial (DM) and ventrolateral (VLM) medulla. In general, stimulating these rostral brain stem pressor areas including the diencephalon (DIC) and rostral pons (RP) produced increases in systemic arterial pressure (SAP). In most of the cases (85%) there were associated changes in the EVRR, predominantly a decrease in EVRR (72%). Stimulation of the midbrain (MB, principally in the periaqueductal grey) produced decreases in SAP and EVRR. Decreases in EVRR was observed in 91% of the DM and VLM stimulations in which an increase in SAP was produced. This EVRR inhibition was essentially unaltered after acute midcollicular decerebration. Increases in EVRR were also observed and occurred more often in the rostral brain stem than in the medulla. Since changes of both EVRR and SAP could be reproduced by microinjection of Glu into the cardiovascular-reactive areas of the brain stem, this suggests that neuronal perikarya in these areas are responsible for both actions. On some occasions, Glu induced changes in EVRR but not in SAP. This effect occurred more frequently in the rostral brain stem than in the medulla. The present data suggest that separate neuron population exist in the brain stem for the integration of SAP and spinal reflexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Glutamate activation of neurons in CV-reactive areas of cat brain stem affects urinary bladder motility

To investigate the interaction between cardiovascular (CV)-reactive areas in the brain stem and urinary bladder (UB) motility, 48 adult cats of either sex were anesthetized intraperitoneally with alpha-chloralose (40 mg/kg) and urethan (400 mg/kg). The changes of UB motility and systemic arterial blood pressure (SAP) were produced by microinjection of sodium glutamate (0.5 M, 100-200 nl) into the pressor, depressor, or vagobradycardiac areas of the brain stem. Stimulation of these CV-reactive areas increased or decreased UB motility. Areas that produced an increase in UB motility listed in decreasing order of effectiveness are locus ceruleus-parabrachial nucleus in the pons, dorsal medulla, dorsal motor nucleus of vagus, and ventrolateral medulla. Areas eliciting a decrease in UB motility listed in decreasing order are gigantocellular tegmental field, parvocellular reticular nucleus, and ambiguus nucleus. Stimulation of other pressor sites in medulla also increased UB motility. Activation of the paramedian reticular nucleus, which consistently produced depressor responses, and activation of raphe nuclei, which produced depressor or pressor responses, consistently decreased UB motility. The integrity of the vagus nerve was not essential for the UB response to brain stimulation. These findings indicate that neuronal mechanisms for controlling UB and CV functions coexist at many sites in the brain stem. At those sites that commonly produce changes in UB motility, the type of UB response (excitation or inhibition) was in the same direction as the change of SAP. However, at some sites responses were inverse. It is not known whether the responses of the UB and CV system are controlled by common or separate populations of neurons at these sites.

Immunohistochemical study of catecholamine enzymes and neuropeptide Y (NPY) in the rostral ventrolateral medulla and bulbospinal projection

The purpose of this study was to determine whether neuropeptide Y (NPY) terminals in the intermediolateral spinal cord originate from the rostral ventrolateral medulla (RVLM). Immunohistochemical staining of tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH), phenylethanolamine-N-methyltransferase (PNMT), and NPY in the rat brainstem and spinal cord were performed in this study in order to examine consequences of lesions of the RVLM and of intracisternal injections of 6-hydroxydopamine (6-OHDA) on catecholamine and NPY immunoreactivity in the intermediolateral column (IML) of rats. In addition, ricin, a retrograde neurotoxin, was applied in the superior cervical ganglion (SCG) to determine its effect on catecholamine and NPY immunoreactivity in the IML. Computer-aided image analysis was used to quantify the immunohistochemical changes in the RVLM and spinal cord. The results demonstrated that many catecholamine- and NPY-containing neurons and/or fibers existed in the RVLM and their terminals were found in the IML. After administration of 6-OHDA intracisternally, the catecholamine and NPY immunoreactivities were decreased both in the brainstem and IML of the spinal cord. Following unilateral microinjection of 6-OHDA into the RVLM, the number of NPY- and catecholamine-containing neurons decreased and there was a reduction in neuron terminals on the ipsilateral side. After injection of ricin into the SCG, the catecholamine and NPY neurons of the medulla were not affected, whereas their terminals in the IML decreased ipsilaterally. These results indicate that most of the catecholamine- and NPY-immunoreactive terminals found in the IML originated in the RVLM. These terminals appear to project towards the superior cervical ganglia.

Differential interactive effects of gliotoxin and MPTP in the substantia nigra and the locus coeruleus in BALB/c mice

We have previously demonstrated that chronic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) infusion to the substantia nigra (SN) and the locus coeruleus (LC) both produce a long-lasting neurotoxicity on dopamine (DA) and norepinephrine (NE) neurons in these two areas, respectively. In the present study, we further examined the toxicity of MPTP in these two areas by using the immunohistochemical method. We have also assessed the role of glia cells in the SN and LC in mediating the toxicity of MPTP. Immunohistochemical results have confirmed the direct toxicity of MPTP in the SN, as revealed by significant decreases of tyrosine hydroxylase (TH)-positive cells in the SN and TH-positive fibers in the striatum. The specific gliotoxin alpha-aminoadipic acid (alpha-AA), when administered to the SN at 48 h interval, partially antagonized DA depletions and behavioral deficits produced by chronic MPTP treatment. When alpha-AA was administered to the SN every 24 h, it completely abolished the toxicity of MPTP. On the other hand, chronic MPTP infusions to the LC significantly decreased DA-beta-hydroxylase-positive cells in this area. When alpha-AA was injected into the LC at 48 h intervals, it did not prevent depletions of NE in the LC and the hippocampus caused by chronic MPTP infusions. It did not protect against the behavioral deficits produced by MPTP, either. When alpha-AA was injected into the LC every 24 h, it only partially prevented the toxicity of MPTP on NE in the LC. It also partially prevented the motor-impairing effect of MPTP; however, it barely protected against MPTP's toxicity on NE in the hippocampus and it did not antagonize the stereotypy deficit produced by chronic MPTP, either. Phasic tremor and rigidity were observed following MPTP infusions to the SN and the LC every day, but these symptoms were less frequently observed during the later experimental stage. Serotonin measures were not significantly altered by these treatments throughout these experiments. Immunoblotting results of glial fibrillary acidic protein (GFAP), a marker protein of astrocytes, have confirmed proper lesions of astrocytes by alpha-AA. These results together suggest that chronic MPTP treatment exerts a direct and long-lasting toxicity on DA neurons along the nigrostriatal pathway and NE neurons along the coeruleus-hippocampal pathway. The neurotoxicity of MPTP is probably mediated through astrocytes in the SN, and may be partly mediated through astrocytes in the LC also. These results imply a role for dendritic uptake of DA and NE in these cell body regions. However, these findings also suggest the possibility of differential mechanisms of MPTP's toxicity in these two areas.

Normal development and the effects of early rhizotomy on spinal systems in the rat

The normal postnatal development of 4 spinal systems was examined in the dorsal horn of the rat spinal cord using histochemical and immunocytochemical techniques. We used thiamine monophosphatase (TMPase), a marker for dorsal root ganglion cells and their projections, a tachykinin, substance P (SP), which is provided by both dorsal root and intrinsic systems, and two markers for descending systems, serotonin (5-HT) and the synthesizing enzyme for noradrenalin, dopamine B-hydroxylase (DBH). The responses of each of these systems to unilateral dorsal lumbosacral rhizotomy on postnatal day 5 was then examined and quantified using image analysis methods to determine whether the extent of plasticity of spinal systems is different after a neonatal lesion than after a comparable lesion made in the adult. Each system differs in development, distribution, and in response to rhizotomy. TMPase is present in the dorsal horn on the day of birth (DPN0) and reaches adult levels of density by 5 days postnatal (DPN5). SP reaction product is present in a distribution similar to the adult in the dorsal horn on DPN0 and reaches adult levels of density by the second postnatal week. 5-HT is present in the dorsal horn on DPN0, shows a laminar distribution at DPN5, and acquires the adult distribution and density at the end of the second week. DBH is present in the dorsal horn on DPN0, acquires the adult distribution at DPN5 and adult levels of density at the end of the second postnatal week. Unilateral lumbosacral rhizotomy in 5 day old rats completely and permanently abolishes TMPase in the dorsal horn by 4 days postoperatively (4DPO). SP is decreased by 4 DPO (9 DPN) but recovers almost completely by 30 DPO. 5-HT is increased by 10 DPO and remains elevated thereafter. DBH is not changed postoperatively. There is shrinkage of lamina I and II by 10 DPO but the recovery of SP and the increase in density of 5-HT staining is proportionally greater than the extent of shrinkage. Therefore, shrinkage contributes to but does not entirely account for either the apparent recovery of SP staining or the increase in density of 5-HT staining. The responses of the TMPase, 5-HT and DBH systems to neonatal rhizotomy are very similar to the response to rhizotomy in adults and there is therefore no evidence for greater plasticity of these systems after neonatal rhizotomy than after adult rhizotomy. The SP systems show more rapid depletion and a greater and more rapid recovery than after adult deafferentation.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasticity of spinal systems after unilateral lumbosacral dorsal rhizotomy in the adult rat

Plasticity of spinal systems in response to lumbosacral deafferentation has previously been described for the cat, by using immunocytochemistry to demonstrate plasticity of tachykinin systems and degeneration methods to demonstrate plasticity of descending systems. In this study, we describe the response to lumbosacral deafferentation in the adult rat. Application of immunocytochemical methods to visualize tachykinins (predominantly substance P magnitude of SP), serotonin (5-HT), and dopamine B-hydroxylase (DBH), the synthesizing enzyme for norepinephrine, permits us to compare the response of SP systems in rat and cat spinal cord and to examine the response of two descending systems, serotoninergic and noradrenergic, to deafferentation. We used image analysis of light microscopic preparations to quantify the immunoreaction product in the spinal cord in order to estimate the magnitude, time course and localization of changes induced by the lesion. The distribution of SP, serotoninergic (5-HT), and noradrenergic staining in the spinal cord of rat is very similar to that of the cat. Unilateral lumbosacral rhizotomy elicits a partial depletion, followed by a partial replacement of tachykinin immunoreactivity in laminae I and II. This response was similar to that described for the cat, although characterized by a longer time course, and, as in the cat, is likely due to plasticity of tachykinin containing interneurons. The same lesion elicits no depletion but a marked and permanent increase in 5-HT immunoreactivity in laminae I and II, which develops more rapidly than the response by the SP system. These results indicate sprouting or increased production of SP and 5-HT in response to deafferentation. No change was seen in DBH immunoreactivity, indicating that the noradrenergic system does not show plasticity in response to deafferentation. Our results demonstrate that dorsal rhizotomy evokes different effects in different systems in the adult spinal cord of the rat and thus suggests that the response of undamaged pathways to partial denervation of their target is regulated rather than random.

Modification of astrocytes in the spinal cord following dorsal root or peripheral nerve lesions

Glial fibrillary acidic protein (GFAP) immunocytochemistry was used to monitor the response of astrocytes in the rat spinal cord to either dorsal root or sciatic nerve lesions. Image analysis methods were used to provide a quantitative correlate of the reactive gliosis. Multiple dorsal root section elicited a rapid increase in GFAP immunoreactivity of astrocytes unilaterally within the spinal cord along the pathway of the degenerating dorsal root axons in the dorsal and ventral horns and this gliosis persisted in the dorsal horn beyond the time at which active phagocytosis of degenerative debris occurred. Labeling of proliferating cells using [3H]thymidine revealed that none of the dividing cells contained detectable GFAP, suggesting that the increased GFAP labeling represents primarily a hypertrophy rather than a proliferation of astrocytes. Comparison of animals that had been deafferented in the early neonatal period with those deafferented as adults indicated that the GFAP immunoreactive response persisted following neonatal lesions but that it was markedly less intense than after adult lesions. Sciatic nerve section in adults does not result in extensive frank degeneration but it does evoke a rapid and marked increase in staining of astrocytes both in the dorsal horn and in the ventral horn. Transganglionic changes in GFAP staining in the dorsal horn occur by 3 days post-operatively, which is much earlier than the time of dorsal root ganglion neuron death caused by the sciatic nerve lesion. These experiments indicate that astrocytes can respond to signals from a variety of changes in neurons, including not only Wallerian degeneration, but also retrograde and transganglionic changes.

Structure of the calcium channel antagonist, nimodipine

Isopropyl 2-methoxyethyl 2,6-dimethyl-4-(3-nitrophenyl)-1,4-dihydro-3,5- pyridinedicarboxylate, C21H26N2O7, Mr = 418.45, orthorhombic, P2(1)2(1)2(1), a = 12.5897 (6), b = 14.6410 (9), c = 11.636 (1) A, V = 2144.8 (2) A3, Z = 4, Dm = 1.29, Dx = 1.30 g cm-3, lambda(Cu K alpha) = 1.54178 A, mu = 7.77 cm-1, F(000) = 888, T = 298 K, R = 0.047 for 1629 observed reflections. The structure of the title compound is similar to that of related analogs, the nitrophenyl ring being roughly normal to the dihydropyridine ring, which is in a boat conformation (N1 is 10.75 degrees out of the C2-C3-C5-C6 plane; C4 is 19.55 degrees out of plane). The 3,5 substituents are in an extended conformation, away from the 2,6 methyl groups. The nitro group is distal to N1. Structure/activity relationships of 1,4-dihydropyridines are discussed in light of this structure.

Comparison of location and binding for the positively charged 1,4-dihydropyridine calcium channel antagonist amlodipine with uncharged drugs of this class in cardiac membranes

The distinctive pharmacokinetic and pharmacodynamic activity of amlodipine, including long onset and duration of activity as a calcium channel antagonist, may be related to its interactions with membranes. We have used X-ray crystallography and small-angle X-ray scattering to examine and compare the crystal structure of amlodipine and its location in cardiac sarcolemmal lipid bilayers with that of uncharged dihydropyridines (DHPs) such as nimodipine. Crystallographic analysis demonstrated that the DHP ring of amlodipine is considerably more planar than that of nimodipine, that amlodipine has a greater torsion angle between the DHP and aryl rings, and that the protonated amino group extends away from the DHP ring structure. Despite the positive charge of amlodipine at physiological pH, membrane electron density profile structures showed amlodipine to have a time-averaged location near the hydrocarbon core/water interface similar to that observed for several uncharged DHPs. However, unlike uncharged DHPs, this location is consistent with an ionic interaction between the protonated amino function of amlodipine and the negatively charged phospholipid headgroup region, in addition to a hydrophobic interaction with the fatty acyl chain region near the glycerol backbone similar to other DHPs. This location may also provide an appropriate conformation and orientation for amlodipine binding to its receptor site at this depth in the membrane. Finally, we have measured the nonspecific partitioning of amlodipine into native sarcoplasmic reticulum membranes from rabbit skeletal muscle and compared these data with those for the uncharged DHPs. The partition coefficient into light sarcoplasmic reticulum for amlodipine was higher than that observed for most uncharged DHPs and rates of incorporation of amlodipine into membranes were very high, as with other DHPs, whereas the "washout time" of amlodipine from these membranes was longer by over 1 order of magnitude. These data suggest differences in membrane interactions for amlodipine, compared with uncharged DHPs, that may be correlated with its novel pharmacodynamic and pharmacokinetic profile.

[Ionic mechanism of noradrenaline-induced membrane potential changes of neurones in toad dorsal root ganglion]

The membrane conductance and reversal potential were determined for neurones in toad dorsal root ganglion (DRG) with intracellular recording technique during depolarization or hyperpolarization induced by noradrenaline (NA). The effects of blocking agents for potassium or calcium channels on NA-induced membrane potential responses were examined. In 15 neurones, the NA-induced depolarization was accompanied by a 32.6% decrease of membrane conductance; in other 4 neurones, the depolarization was accompanied by an initial increase and subsequent decrease in membrane conductance. The NA hyperpolarization was associated with an increase of membrane conductance by 16.2% (n = 8). The mean reversal potential of NA-induced depolarization was -88.5 +/- 0.9 mV (means +/- SE, n = 4). The NA-induced hyperpolarization was nullified at -89 to -92 mV of membrane potentials (n = 3). Tetraethylammonium superfusion enhanced NA depolarization amplitude by 73.7 +/- 11.9% (means +/- SE, n = 7) and depressed NA hyperpolarization amplitude by 40.5% (n = 4). Intracellular injection of CsCl increased phenylephrine-induced depolarization by 34.5% (n = 4). MnCl2 superfusion decreased the amplitudes of NA-induced depolarization by 50.5 +/- 9.9% (means +/- SE, n = 10), and of NA-induced hyperpolarization by 89.5 +/- 4.9% (means +/- SE, n = 7) respectively. The results suggest that the depolarization or hyperpolarization induced by NA might be mediated by the alteration in activation of K+ or Ca2+ channels.

Effects of stellate ganglionectomy on the cat cardiovascular function

The effects of stellate ganglionectomy on cardiovascular function were assessed in pentobarbital-anesthetized cats. A right stellectomy produced much more profound bradycardiac effects than a left stellectomy. This finding demonstrated that the stellate ganglion exerted a lateralized influence on heart beat in the cat. The cardiovascular response of intact cats to phase 4 (overshoot) of the Valsalva-like maneuver (VM) was reflex bradycardia. In response to VM, however, reflex bradycardia was completely abolished by a right or bilateral stellectomy, or by pretreatment with propranolol, but not by a left stellectomy alone or with phentolamine. The data indicated that the right stellate ganglion in cats makes a major contribution to cardiovascular control, especially over reflex bradycardia mechanisms.

Vagal cardioinhibitory area in and around the caudal inferior olivary nucleus of cats. II. Modulatory actions

In chloralose-urethane anesthetized cats, bilateral destruction of the caudal part of the inferior olivary nucleus (ION) produced neither apparent alteration of the basal arterial blood pressure and heart rate, nor discernible influence on the degree of the induced reflex bradycardia by phenylephrine and reflex tachycardia by nitroglycerin. Apart from directly producing cardioinhibition, stimulation of the ION was capable of interacting synergistically with the reflex bradycardia and antagonistically with the reflex tachycardia. Stimulation of the ION was also capable of potentiating the bradycardias induced from stimulating other cardioinhibitory areas, including the ION of the other side and the gigantocellular reticular nuclei of both sides of the medulla. These interactions were still feasible when one vagus nerve remained intact, but not after both nerves were cut. The results suggest that the ION may not be a primary component of the neural loops subserving the baroreceptor reflex arch, but instead, assumes modulatory actions to this reflex mechanism via both vagus nerves.

Retrograde localization of the innervation of the middle cerebral artery with horseradish peroxidase in cats

The innervation of the middle cerebral artery (MCA) of the cat was studied by applying horseradish peroxidase (HRP) to the wall of the right MCA. After a survival period of 48 to 72 hours, the bilateral superior cervical ganglia, middle cervical ganglia, stellate ganglia, T-4 sympathetic paravertebral ganglia, geniculate ganglia, semilunar ganglia, nodose ganglia, and brain stem including midbrain, pons, and medulla oblongata were removed to be processed with tetramethyl benzidine. HRP-labeled neurons were found in the ipsilateral superior cervical ganglion, semilunar ganglion, and dorsal raphe nucleus. The other areas did not have HRP activity. The results suggest that the adrenergic nerves innervating the MCA originate in the ipsilateral superior cervical ganglion, the sensory nerves originate in the ipsilateral semilunar ganglion, and the serotonergic nerves originate in the ipsilateral dorsal raphe nucleus. Cerebral arterial constriction may relate to the intrinsic (intracerebral) neurogenic pathway involving the trigeminal nerve and the dorsal raphe nucleus.