Biomedical subjects

K N Westlund

Publications and source records attributed to K N Westlund.

At least 19 recordsLinked to original sources

PubMed2005

Exogenous Bcl-xL fusion protein spares neurons after spinal cord injury.

Spinal cord injury (SCI) induces neuronal death, including apoptosis, which is completed within 24 hr at and around the impact site. We identified early proapoptotic transcriptional changes, including upregulation of proapoptotic Bax and downregulation of antiapoptotic Bcl-xL, Bcl-2, and Bcl-w, using Affymetrix DNA microarrays. Because Bcl-xL is the most robustly expressed antiapoptotic Bcl-2 molecule in adult central nervous system, we decided to characterize better the effect of SCI on Bcl-xL expression. We found Bcl-xL expressed robustly throughout uninjured spinal cord in both neurons and glia cells. We also found Bcl-xL localized in different cellular compartments: cytoplasmic, mitochondrial, and nuclear. Bcl-xL protein levels decreased in the cytoplasm and mitochondria 2 hr after SCI and persisted for 24 hr. To test the contribution of proapoptotic decreases in Bcl-xL to neuronal death, we augmented endogenous Bcl-xL levels by administering Bcl-xL fusion protein (Bcl-xL FP) into injured spinal cords. Bcl-xL FP significantly increased neuronal survival, suggesting that SCI-induced changes in Bcl-xL contribute considerably to neuronal death. Because Bcl-xL FP increases survival of dorsal horn neurons and ventral horn motoneurons, it could become clinically relevant in preserving sensory and motor functions after SCI.

Animals↗

PubMed2004

Excitatory amino acids, TNF-alpha, and chemokine levels in synovial fluids of patients with active arthropathies.

The aim of this study was to assess the synovial fluid (SF) neurotransmitter excitatory amino acid (EAA) levels, including glutamate (Glu) and aspartate (Asp), in the context of SF levels of other amino acids, TNF-alpha and chemokines from patients with active arthropathies. The SF was collected from patients with active rheumatoid arthritis (RA), gout, or osteoarthritis (OA). The SF samples were analysed for levels of neurotransmitters glutamate and aspartate, tumour necrosis factor-alpha (TNF-alpha), Regulated upon Activation Normally T-cell Expressed and Secreted (RANTES), macrophage inhibitory factor-1 alpha (MIP-1alpha) and interleukin 8 (IL-8). SF WBC counts were also determined. Correlations between SF EAA, TNF-alpha and chemokines were determined by the Pearson product-moment correlation. Primary cultures derived from SF from active RA and gout patients were incubated with added l-glutamate, to assess if exposure to Glu could increase TNF-alpha levels. There were significant elevations in SF EAA, SF TNF-alpha and SF RANTES in RA patients compared to gout or OA patients. Significant correlations between SF EAA and SF RANTES, MIP-1alpha and IL-8 levels were seen, and SF EAA and SF TNF-alpha or SF WBC levels approached significance. Addition of exogenous neurotransmitter glutamate significantly increased TNF-alpha levels in primary cell cultures derived from RA and gout patients. The SF neurotransmitter EAA levels significantly correlated to selected SF chemokine levels, in clinically active RA, gout and OA patients, independent of disease. Added Glu resulted in significantly increased TNF-alpha levels in primary synovial cell cultures. These data expand the relationship of SF neurotransmitter EAA levels to SF cytokines and chemokines in patients with clinically active arthritis, and suggest that neurotransmitters Glu and Asp contribute to peripheral inflammatory processes.

Adult↗

PubMed2003

Comparison of microdialysis and push-pull perfusion for retrieval of serotonin and norepinephrine in the spinal cord dorsal horn.

Both push-pull and microdialysis methods are utilized to measure norepinephrine and serotonin in the dorsal horn of the spinal cord. This experiment was designed to determine which technique is better for measurement of norepinephrine and serotonin in the spinal cord and also to determine if the samples are best collected with or without perchloric acid. Sample stability and an assay validation for precision, limit of quantification, and limit of detection were also performed. Push-pull or microdialysis catheters were placed transversely through the dorsal horn and the catheter was perfused with artificial cerebrospinal fluid. Noxious pinch (20 s/min for 10 min) was used to evoke a change in the concentration of catecholamines. Samples were collected before, during and after pinch. No basal concentrations of epinephrine and serotonin were found with microdialysis. Although basal concentrations of norepinephrine were measured by microdialysis, there was no change in response to noxious pinch. The push-pull technique coupled with collection of samples without perchloric acid showed that significant increases in serotonin and norepinephrine are measurable in response to noxious pinch. In contrast, when samples were collected with perchloric acid present there was no change in serotonin or norepinephrine in response to pinch. The stability of catecholamines is greatly affected by perchloric acid such that there is a near complete loss of ability to detect serotonin and norepinephrine by 24 h in samples collected by push-pull. In contrast, samples collected without perchloric acid showed only a 20% reduction in concentration by 24 h. Even without perchloric acid, by 1 wk there was a 50% or greater loss in the concentrations of norepinephrine in push-pull samples. Thus, to measure changes in catecholamines in the dorsal horn, push-pull collected without perchloric provides measurable, reliable and valid results if analyzed by high performance liquid chromatography within 24 h.

Animals↗

PubMed2002

DNA microarray analysis of the contused spinal cord: effect of NMDA receptor inhibition.

Spinal cord injury (SCI)-induced neurodegeneration leads to irreversible and devastating motor and sensory dysfunction. Post-traumatic outcomes are determined by events occurring during the first 24 hours after SCI. An increase in extracellular glutamate concentration to neurotoxic levels is one of the earliest events after SCI. We used Affymetrix DNA oligonucleotide microarrays (with 1,322 DNA probes) analysis to measure gene expression in order to test the hypothesis that SCI-induced N-methyl-D-aspartate (NMDA) receptor activation triggers significant postinjury transcriptional changes. Here we report that SCI, 1 hour after trauma, induced change in mRNA levels of 165 genes and expression sequence tags (ESTs). SCI affected mRNA levels of those genes that regulate predominantly transcription factors, inflammation, cell survival, and membrane excitability. We also report that NMDA receptor inhibition (with -(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine hydrogen maleate [MK-801]) reversed the effect of SCI on about 50% of the SCI-affected mRNAs. Especially interesting is the finding that NMDA receptor activation participates in the up-regulation of inflammatory factors. Therefore, SCI-induced NMDA receptor activation is one of the dominant, early signals after trauma that leads to changes in mRNA levels of a number of genes relevant to recovery processes. The majority of MK-801 effects on the SCI-induced mRNA changes reported here are novel. Additionally, we found that the MK-801 treatment also changed the mRNA levels of 168 genes and ESTs that had not been affected by SCI alone, and that some of their gene products could have harmful effects on SCI outcome.

Animals↗

PubMed2001

Responses of rat dorsal column neurons to pancreatic nociceptive stimulation.

Our previous study has shown that the postsynaptic dorsal column pathway is involved in transmission of pancreatic nociceptive information from the spinal cord to the thalamus. The aim of the present study was to characterize the neuronal responses in the dorsal column nuclei of the rat to pancreatic nociceptive stimulation. Brief application of bradykinin (10 microg/ml, 20s) to the surface of the pancreas resulted in a significantly increased firing rate in approximately 10% of neurons recorded. In conclusion, pancreatic nociceptive information relayed to the dorsal column nuclei is transmitted from the spinal cord through the dorsal columns.

Animals↗

PubMed2001

Effects of baclofen on colon inflammation-induced Fos, CGRP and SP expression in spinal cord and brainstem.

The present study demonstrates sites of expression for Fos protein in the brainstem and lumbosacral spinal cord of rats subjected to mustard oil irritation of the colon. The protective effect of baclofen, a selective GABA(B) receptor agonist, on the induced Fos protein increases was determined. Mustard oil injected into the lumen of the colon produces an acute site-specific inflammation. Immunocytochemical localization of Fos protein in neuronal nuclei was evident after 1 h, was greatest at 2 h and was still evident but declining at 8 h. In the spinal cord the majority of Fos labeled neurons were localized in the superficial laminae of lumbar (L6) cord with more found in the sacral (S1) cord. Some labeled neurons were also found in the deeper spinal laminae, intermediolateral nucleus and around lamina X. Brainstem sites expressing Fos included the nucleus of the solitary tract in the medulla, parabrachial, locus coeruleus, pontine and caudal dorsal raphe nuclei and periaqueductal gray. Weak Fos protein labeling existed in a few cells in vehicle control animals. Systemic administration of the GABA(B) receptor agonist, baclofen (10 mg/kg, i.p.), significantly reduced Fos expression in the spinal cord after mustard oil treatment but significantly increased the relative number of nuclei labeled in the nucleus of the solitary tract. Baclofen also significantly decreases dorsal horn CGRP immunoreactivity relative to the increased levels seen after inflammation of the colon. The SP content increases observed after inflammation of the colon were not altered by baclofen. These data suggest that: (1) neurons in regions important for nociceptive transmission, descending inhibitory control and autonomic control are activated by noxious stimulation of the colon, and (2) baclofen specifically reduces Fos expression in the superficial dorsal horn of the spinal cord induced by nociceptive afferent input.

Animals↗

PubMed2001

The role of the dorsal column pathway in visceral nociception.

Neurosurgeons have successfully used punctate midline myelotomy to relieve visceral cancer pain in human patients. Animal experiments demonstrate a visceral nociceptive pathway in the posterior column that is more effective than the spinothalamic tract in activating thalamic neurons, eliciting behavioral responses and triggering increases in regional cerebral blood flow. This visceral nociceptive pathway involves postsynaptic dorsal column neurons in the central, visceral processing region of the spinal cord. Axons from the sacral cord ascend near the midline and from the thoracic cord at the junction of the gracile and cuneate fasciculi.

Afferent Pathways↗

PubMed2001

Do nociceptive signals from the pancreas travel in the dorsal column?

A midline dorsal column lesion has been shown to be an effective surgical treatment for the relief of pelvic visceral pain in patients. The aim of this study was to examine the effectiveness of a dorsal column lesion upon: (i) increased electrophysiological responses of neurons in the ventral posterolateral thalamic nucleus in anesthetized rats evoked by the application of bradykinin to the surface of the pancreas, and (ii) pain-related behaviors observed after pancreatic infusion with bradykinin. In rats anesthetized with pentobarbital, recordings from individual thalamic neurons were made using tungsten electrodes. Brief application of bradykinin (10 microg/ml) to the surface of the pancreas resulted in an increased firing rate in approximately 20% of neurons recorded. A dorsal column lesion or intrathecal administration of morphine greatly reduced the excitatory effects of pancreatic bradykinin application on thalamic neurons. In a separate group of rats, bradykinin was infused into the pancreas through a previously implanted catheter resulting in a decrease in exploratory behavior and an increase in other pain-related behaviors, e.g. licking of the abdomen. A dorsal column lesion made prior (1 week) to the bradykinin infusion reduced the decrease in exploratory behavior but did not return exploratory behavior to control levels. In conclusion, nociceptive information relayed to the thalamus about the pancreas is transmitted from the spinal cord through the dorsal columns, possibly by the post-synaptic dorsal column pathway. However, the dorsal column pathway may not be the sole route for relaying information about noxious stimulation of the pancreas, particularly that impacting complex behavioral responses.

Analgesics, Opioid↗

PubMed2001

Arthritic calcitonin/alpha calcitonin gene-related peptide knockout mice have reduced nociceptive hypersensitivity.

Peripheral inflammation induced with a knee joint injection of a mixture of kaolin/carrageenan (k/c) produces primary and secondary hyperalgesia. Inflammatory pain is thought to involve a variety of transmitters released from nerve terminals, including amino acids, substance P (SP) and calcitonin gene-related peptide (CGRP). In the present study, mice deficient in the calcitonin/alpha CGRP gene (CGRP(-/-)) displayed normal responses to noxious stimuli. However, the CGRP knockout mice failed to demonstrate development of secondary hyperalgesia after induction of knee joint inflammation in two tests that assess central sensitization, through testing at sites remote from the primary insult. Nociceptive behavioral responses were assessed using the hot-plate test and paw withdrawal latency (PWL) to radiant heat applied to the hindpaw. The CGRP(-/-) mice showed no signs of secondary hyperalgesia after development of knee joint inflammation, while the expected significant decrease in the PWL was observed in the CGRP(+/+) mice as control. The CGRP(-/-) mice also had a prolonged rather than a shortened response latency in the hot-plate test 4 h after knee joint injection of k/c. Immunohistological study showed that CGRP-like immunoreactivity (CGRP-LI) was absent in the spinal cord and dorsal root ganglia taken from the CGRP(-/-) mice. These results indicate that endogenous CGRP plays an important role in the plastic neurogenic changes occurring in response to peripheral inflammatory events including the development of nociceptive behaviors.

Animals↗

PubMed2001

Bcl-xL expression after contusion to the rat spinal cord.

After contusion-derived spinal cord injury, (SCI) there is localized tissue disruption and energy failure that results in early necrosis and delayed apoptosis, events that contribute to chronic central pain in a majority of patients. We assessed the extent of contusion-induced apoptosis of neurons in a known central pain-signaling pathway, the spinothalamic tract (STT), which may be a contributor to SCI-induced pain. We observed the loss of STT cells and localized increase of DNA fragmentation and cytoplasmic histone-DNA complexes, which suggested potential apoptotic changes among STT neurons after SCI. We also showed SCI-associated changes in the expression of the antiapoptotic protein Bcl-xL, especially among STT cells, consistent with the hypothesis that Bcl-xL regulates the extent of apoptosis after SCI. Apoptosis in the injured spinal cord correlated well with prompt decreases in Bcl-xL protein levels and Bcl-xL/Bax protein ratios at the contusion site. We interpret these results as evidence that regulation of Bcl-xL may play a role in neural sparing after spinal injury and pain-signaling function.

Animals↗

PubMed2000

Visceral nociception.

Visceral pain is of great concern to the medical community because it remains particularly resistant to current clinical treatments. A serendipitous and initially unexplainable clinical finding that a punctate midline dorsal column lesion is effective in eliminating visceral pain, however, has initiated a resurgence of interest in the study of the basic mechanisms of visceral nociception. Clinical and anatomic findings have determined that visceral pain either of thoracic or pelvic origin can be relieved by carefully placed lesions directed at the lateral edge or the medial edge of the gracile fasciculus, respectively. Studies are demonstrating that visceral pain is quite unique from cutaneous pain.

Afferent Pathways↗

PubMed2000

Amino acid release into the knee joint: key role in nociception and inflammation.

This study examined the release of several amino acids after induction of knee joint inflammation in rats using kaolin and carrageenan. During the initial 10-min collection after knee joint injection with the irritants, the concentration of glutamate and the nitric oxide metabolites, arginine and citrulline, doubled. This increase persisted for at least two hours. During the same time period aspartate concentrations remained unchanged. Direct knee joint administration of lidocaine prevented the increases in amino acid concentration measurable by microdialysis probe inserted into the joint. These data suggest the possibility that glutamate may be released by neuronal endings in the joint.

Amino Acids↗

PubMed2000

Rodent model of chronic central pain after spinal cord contusion injury and effects of gabapentin.

Spinal cord injury (SCI) often results in abnormal pain syndromes in patients. We present a recently developed SCI mammalian model of chronic central pain in which the spinal cord is contused at T8 using the NYU impactor device (10-g rod, 2.0-mm diameter, 12.5-mm drop height), an injury which is characterized behaviorally as moderate. Recovery of locomotor function was assessed with an open field test and scored using the open field test scale (BBB scale). Somatosensory tests of paw withdrawal responses accompanied by supraspinal responses to both mechanical punctate (von Frey hairs) and nonpunctate (4 mm diameter blunt probe) as well as thermal (radiant heat) peripheral stimuli were performed. Comparisons at the level of the individual animal between precontusion and postcontusion responses indicated significant increases in reactions to low threshold punctate mechanical stimuli, non-punctate stimuli and thermal stimuli (p < 0.05). To demonstrate the validity of this model as a central pain model, gabapentin, an agent used clinically for central pain, was given i.p. at 10 or 30 mg/kg. Gabapentin treatment significantly and reversibly changed the responses, consistent with the attenuation of the abnormal sensory behavior, and the attenuated responses lasted for the duration of the drug effect (up to 6 h). These results support the use of the spinal contusion model in the study of chronic central pain after SCI.

Acetates↗

PubMed2000

Increased blood pressure in alpha-calcitonin gene-related peptide/calcitonin gene knockout mice.

Nerves that contain calcitonin gene-related peptide (CGRP) are components of the sensory nervous system. Although these afferent nerves have traditionally been thought to sense stimuli in the periphery and transmit the information centrally, they also have an efferent vasodilator function. Acute administration of a CGRP receptor antagonist increases the blood pressure (BP) in several models of hypertension, which indicates that this potent vasodilator plays a counterregulatory role to attenuate the BP increase in these settings. To determine the role of this peptide in the long-term regulation of cardiovascular function, including hypertension, we obtained mice that have a deletion of the alpha-calcitonin gene-related peptide (alpha-CGRP) gene. Although the beta-calcitonin gene-related peptide (beta-CGRP) gene is intact in these mice, alpha-CGRP is by far the predominant species of CGRP produced in dorsal root ganglia (DRG) sensory neurons. Initially, we examined the effect of deletion of the alpha-CGRP on baseline BP and beta-CGRP and substance P mRNA expression. Systolic BP was significantly higher in the knockout mice (n=7) compared with wild-type in both male (160+/-6.1 vs 125+/-4.8 mm Hg) and female (163+/-4.8 vs 135+/-33 mm Hg) mice. Next, groups (n=7) of knockout and wild-type mice had catheters surgically placed in the right carotid artery for mean arterial pressure recording. With the animals fully awake and unrestrained, the knockout mice displayed an elevated mean arterial pressure compared with wild-type in both male (139+/-4.9 vs 118+/-4.9 mm Hg) and female (121+/-3.4 vs 107+/-3.1 mm Hg) mice. Northern blot analysis of DRG RNA samples confirmed the absence of alpha-CGRP mRNA in the knockout mice. Substance P mRNA content in DRG was unchanged between the 2 groups; however, beta-CGRP mRNA levels were reduced 2-fold in the knockout mice. These results indicate for the first time that alpha-CGRP may be involved in the long-term regulation of resting BP and suggest that these mice are particularly sensitive to challenges to BP homeostasis because of the loss of a compensatory vasodilator mechanism.

Animals↗

PubMed2000

Punctate midline myelotomy for the relief of visceral cancer pain.

OBJECT: This study offers clinical support for the concept that neurosurgical interruption of a midline posterior column pathway by performing a punctate midline myelotomy (PMM) provides significant pain relief without causing adverse neurological sequelae in cancer patients with visceral pain refractory to other therapies. METHODS: A PMM of the posterior columns was performed in six cancer patients in whom visceral pain had been refractory to other therapies. The cause of the visceral pain was related to residual, progressive, or recurrent local cancer or postirradiation effects. Clinical efficacy of the procedure was examined by comparing patient pain ratings and narcotic usage pre- and post-PMM. Follow-up periods ranged from 3 to 31 months. Examination of the results indicates a significant reduction in pain ratings as well as a significant reduction in daily narcotic use. No adverse neurological effects were observed. One spinal cord has been recovered for postmortem examination. CONCLUSIONS: These findings provide corroborating clinical evidence for the existence of a newly recognized midline posterior column pathway that mediates the perception of visceral pelvic and abdominal pain. Preliminary data indicate that significant pain relief can be obtained following PMM with minimal neurological morbidity and suggest that the procedure may provide an alternative treatment modality for cancer-related pain in patients in whom adequate pain control with narcotics cannot be achieved or narcotic side effects cannot be tolerated.

Abdominal Neoplasms↗

PubMed2000

Excitatory amino acid profiles of synovial fluid from patients with arthritis.

OBJECTIVE: Previous studies in an experimental synovitis model in rats determined that administration of glutamate and aspartate into the joint produces hyperalgesic responses, while their receptor antagonists provide protection against the development of a hyperalgesic state. We examined concentrations of amino acids in synovial fluid (SF) to determine if increases might be relevant to human joint pathology. METHODS: One hundred forty-four repository SF samples from patients undergoing diagnostic or therapeutic arthrocentesis and 14 SF samples from 7 cadavers were analyzed by high pressure liquid chromatography and compared as arthritic and control cohorts. RESULTS: Compared to the average concentrations from the autopsy cases, the excitatory amino acids (EAA) glutamate and aspartate in SF from patients with synovitis were 54 and 28 times higher, respectively. Increases for all other amino acids ranged from 3 to 18-fold. The values for glutamate and aspartate were significantly higher than the mean increase for other amino acids compared using unpaired t tests (p < 0.0001). The mean ratio of glutamate and aspartate elevations over the mean increase for other amino acids was 4-fold and 2-fold, respectively. The EAA were highest in Reiter's, infectious arthropathies, and systemic lupus erythematosus, but did not appreciably segregate to diagnosis or SF white blood cell count. CONCLUSION: Our data provide evidence of increased glutamate and aspartate in the SF of humans with active arthritis, suggesting that glutamate mediated events may contribute to the pathogenesis of human arthritic conditions.

Adolescent↗

PubMed1999

Ascending projections from the area around the spinal cord central canal: A Phaseolus vulgaris leucoagglutinin study in rats.

A single small iontophoretic injection of Phaseolus vulgaris leucoagglutinin labels projections from the area surrounding the spinal cord central canal at midthoracic (T6-T9) or lumbosacral (L6-S1) segments of the spinal cord. The projections from the midthoracic or lumbosacral level of the medial spinal cord are found: 1) ascending ipsilaterally in the dorsal column near the dorsal intermediate septum or the midline of the gracile fasciculus, respectively; 2) terminating primarily in the dorsal, lateral rim of the gracile nucleus and the medial rim of the cuneate nucleus or the dorsomedial rim of the gracile nucleus, respectively; and 3) ascending bilaterally with slight contralateral predominance in the ventrolateral quadrant of the spinal cord and terminating in the ventral and medial medullary reticular formation. Other less dense projections are to the pons, midbrain, thalamus, hypothalamus, and other forebrain structures. Projections arising from the lumbosacral level are also found in Barrington's nucleus. The results of the present study support previous retrograde tract tracing and physiological studies from our group demonstrating that the neurons in the area adjacent to the central canal of the midthoracic or lumbosacral level of the spinal cord send long ascending projections to the dorsal column nucleus that are important in the transmission of second-order afferent information for visceral nociception. Thus, the axonal projections through both the dorsal and the ventrolateral white matter from the CC region terminate in many regions of the brain providing spinal input for sensory integration, autonomic regulation, motor and emotional responses, and limbic activation.

Animals↗

PubMed1999

A visceral pain pathway in the dorsal column of the spinal cord.

A limited midline myelotomy at T10 can relieve pelvic cancer pain in patients. This observation is explainable in light of strong evidence in support of the existence of a visceral pain pathway that ascends in the dorsal column (DC) of the spinal cord. In rats and monkeys, responses of neurons in the ventral posterolateral thalamic nucleus to noxious colorectal distention are dramatically reduced after a lesion of the DC at T10, but not by interruption of the spinothalamic tract. Blockade of transmission of visceral nociceptive signals through the rat sacral cord by microdialysis administration of morphine or 6-cyano-7-nitroquinoxaline-2,3-dione shows that postsynaptic DC neurons in the sacral cord transmit visceral nociceptive signals to the gracile nucleus. Retrograde tracing studies in rats demonstrate a concentration of postsynaptic DC neurons in the central gray matter of the L6-S1 spinal segments, and anterograde tracing studies show that labeled axons ascend from this region to the gracile nucleus. A similar projection from the midthoracic spinal cord ends in the gracile and cuneate nuclei. Behavioral experiments demonstrate that DC lesions reduce the nocifensive responses produced by noxious stimulation of the pancreas and duodenum, as well as the electrophysiological responses of ventral posterolateral neurons to these stimuli. Repeated regional blood volume measurements were made in the thalamus and other brain structures in anesthetized monkeys in response to colorectal distention by functional MRI. Sham surgery did not reduce the regional blood volume changes, whereas the changes were eliminated by a DC lesion at T10.

Afferent Pathways↗