Biomedical subjects

L Brundin

Publications and source records attributed to L Brundin.

At least 19 recordsLinked to original sources

PubMed2006

No signs of immunoactivation in the cerebrospinal fluid during treatment with infliximab.

Neuroinflammatory (demyelinating) disease is a rare but feared complication of treatment with anti-tumour necrosis factor (TNF)alpha in patients with polyarthritis. In this study, blood and cerebrospinal fluid markers of inflammation were analysed in 10 people with polyarthritis before and during treatment with infliximab. An increased systemic expression of interferon (IFN)gamma was detected. Systemic administration of IFNgamma is known to exacerbate multiple sclerosis. However, the present study failed to detect signs of inflammation in the cerebrospinal fluid samples-that is, pleocytosis, oligoclonal immunoglobulin G bands, increased expression of IFNgamma, TNFalpha or interleukin 10, or increased levels of nitric oxide oxidation products. Our initial hypothesis, that the few cases of clinical neuroinflammatory disorders observed during treatment of polyarthritis with anti-TNFalpha represent the extreme end of a commonly occurring minor intrathecal immune activation, which in most cases does not give any overt neurological dysfunction, was not supported. Induction of systemic IFNgamma production may still be relevant in neuroinflammation associated with treatment with anti-TNFalpha.

Adult↗

PubMed2001

Increased levels of proinflammatory cytokines and nitric oxide metabolites in neuropsychiatric lupus erythematosus.

OBJECTIVE: To investigate systemic and intrathecal production of proinflammatory cytokines in relation to cerebrospinal fluid (CSF) nitric oxide (NO) release in patients with neuropsychiatric lupus erythematosus (NPLE). METHODS: Thirty patients with NPLE rated as mild, moderate, or severe were studied and CSF was obtained from 21 of these. Cytokine mRNA expressing cells were detected by in situ hybridisation. Soluble cytokines were assessed by enzyme linked immunosorbent assay (ELISA). Nitrite and nitrate were determined by capillary electrophoresis. RESULTS: Patients with NPLE had high numbers of lymphocytes expressing mRNA for tumour necrosis factor alpha (TNFalpha), interferon gamma, and interleukin 10 in blood. The number of peripheral blood TNFalpha mRNA positive cells correlated strongly with the level of NO metabolites in the CSF (r(2)=0.69). Both the number of peripheral blood mononuclear cells expressing mRNA for TNFalpha as well as the CSF level of NO metabolites correlated with NPLE disease severity. CONCLUSION: These data suggest that increased peripheral production of proinflammatory cytokines such as TNFalpha may contribute both to an increased production of NO in the central nervous system and to generation of clinical NPLE. The data also support the possibility that measurements of NO metabolites in CSF may be of value in the diagnosis of neurological symptoms related to SLE.

Adult↗

PubMed2000

Noise-induced aspartate and glutamate efflux in the guinea pig cochlea and hearing loss.

Aspartate and glutamate were monitored in the scala tympani of the guinea pig cochlea using in vivo microdialysis before and during noise exposure. Moderate level broad band noise [105 dB sound pressure level (SPL), 30 min] neither altered the levels of aspartate or glutamate, nor auditory brainstem response (ABR) thresholds. High level noise exposure (135 dB SPL, 30 min) caused a large increase in aspartate (330%), a smaller increase in glutamate (150%), and a permanent ABR threshold shift of 60-75 dB between 2.0 and 12.5 kHz. Morphological analysis of the cochlea revealed a collapse of supporting structures, swelling of the afferent dendrites under the inner hair cells, and outer hair cell loss. Pretreatment with the NMDA antagonist, MK 801 (1 mg/kg body weight, i.p.) 1 h before noise exposure protected the afferent dendrites from swelling but did not protect the collapse of supporting structures, outer hair cell loss, or auditory thresholds. In conclusion, the noise-induced increase in aspartate and glutamate release in the cochlea and the protective effect of NMDA antagonism suggest that these two neurotransmitters are involved in noise-induced hearing loss.

Acoustic Stimulation↗

PubMed1999

Visualization of nitric oxide formation in cell cultures and living tissue.

We have visualized nitric oxide (NO) released from cell cultures and living tissue. NO was visualized by a reaction with luminol and hydrogen peroxide to yield photons which were counted using a microscope coupled to a photon counting camera. Murine macrophages were activated with interferon-gamma (IFN-gamma) and endotoxin (LPS). Cultured endothelial cells were stimulated with bradykinin, and neurones in the guinea-pig myenteric plexus and the rabbit hypogastric nerve trunk were electrically stimulated. There was a marked increase in photons emitted from the cultured cells as well as from the living tissues during stimulation. The stimulation-induced photon emission was markedly reduced by inhibition of nitric oxide synthase (NOS); removal of L-arginine from the medium also decreased photon counts. The present method allowed integration times in the order of minutes to improve signal-to-noise ratio. However, the high sensitivity of this method also makes it possible to generate an image in seconds, allowing the production of real time films. Photon emission was enhanced under conditions known to increase NO production, and diminished in the presence of NO inhibitors. Thus, this method has demonstrated specificity for the L-arginine:NO pathway from a wide range of biological sources such as cultured cells and living tissues, and has the potential for real time imaging of NO formation, with high temporal and spatial resolution.

Animals↗

PubMed1999

Increased intrathecal nitric oxide formation in multiple sclerosis; cerebrospinal fluid nitrite as activity marker.

Nitric oxide is formed from L-arginine by a family of enzymes: nitric oxide synthase (NOS). The inducible nitric oxide synthase is activated by cytokines and it has been suggested that activation of the enzyme gives rise to neurotoxic levels of reactive nitrogen oxides. This enzyme has been shown to be localized in multiple sclerosis (MS) lesions but the role of nitric oxide formation in the pathogenesis of MS is still unclear. Using capillary electrophoresis, we have analysed nitrite and nitrate in cerebrospinal fluid (CSF) and demonstrate increased levels of reactive nitrogen products in 17 patients with MS. The total levels of oxidized nitrogen products were significantly elevated in MS patients when compared with controls. In patients with active MS, nitrite levels were significantly increased when compared with controls and patients in remission. This is supportive of NOS induction in MS. We suggest that capillary electrophoresis analysis of nitrite and nitrate in CSF could provide a clinically useful way to determine disease activity in MS.

Adult↗

PubMed1998

Central nervous system nitric oxide formation in cerebral systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is an inflammatory disease in which up to two thirds of the patients present neurological symptoms. The diagnosis of the disease is based on clinical findings and the presence of autoantibodies, and the pathogenesis is unclear. The purpose of this study was to determine if the pathogenesis was partly mediated via nitric oxide (NO) formation. Cerebrospinal fluid (CSF) samples from 15 patients with cerebral SLE were analyzed for the NO metabolites nitrite and nitrate using capillary electrophoresis. The severity of neurological symptoms was scored by dividing the patients into two groups with either mild or moderate/severe CNS involvement. All patients with cerebral SLE showed increased levels of NO metabolites. In CSF, there was a relationship between signs of NO production and clinical results showing that increased levels of nitrite and nitrate were associated with more severe neurological symptoms. These findings may shed new light on the pathogenesis of cerebral SLE, and analysis of nitrate and nitrate may prove to be of value in monitoring the activity of the disease.

Brain Diseases↗

PubMed1998

Sound-evoked efflux of excitatory amino acids in the guinea-pig cochlea in vitro.

We have used the perfused guinea-pig temporal-bone preparation to study the sound-evoked efflux of aspartate and glutamate, which are putative afferent transmitters in the cochlea. The cochlea was stimulated with white noise at 89, 95, and 101 dB SPL. Cochlear function was monitored by recording the endocochlear potential, the cochlear microphonic, and the summating potential. In silence, there was a low basal efflux of both amino acids. A significant and intensity dependent sound-evoked efflux of aspartate was observed at all levels, whereas a significant efflux of glutamate was found only at the 101 dB SPL level. Immunohistochemistry of sections from the organ of corti showed an ubiquitous distribution of glutamate-like immunoreactivity in the sensory organ and ganglion, whereas aspartate-like immunoreactivity was found in the region of the inner hair cells and in the spiral ganglion. In view of these findings, we suggest that not only glutamate, but also aspartate may have a neurotransmitter role in the afferent pathway of the cochlea.

Acoustic Stimulation↗

PubMed1998

The role of nitric oxide in bacillus Calmette-Guérin mediated anti-tumour effects in human bladder cancer.

Bacillus Calmette-Guérin (BCG) has been used for many years to treat cancer of the urinary bladder. It constitutes effective intravesical therapy of carcinoma in situ and recurrent superficial bladder cancer. Although the mechanism of action is unknown, most evidence suggests an immune-mediated mechanism. BCG treatment is known to increase cytokine production in the urinary bladder. As cytokines may induce nitric oxide synthase (NOS) activity and as nitric oxide (NO) exerts cytotoxic effects on tumour cells, we investigated the role of NO in BCG-mediated anti-tumour activity. Here we demonstrate a marked induction of both calcium-dependent and calcium-independent NOS activity in the human urinary bladder after BCG treatment. The presence of NOS in the urothelial cells was also demonstrated by the use of immunohistochemistry. Furthermore, patients treated with BCG showed a 30 times higher production of gaseous NO as measured in the urinary bladder by chemiluminescence. Finally, NO donors exerted cytotoxic effects on bladder cancer cell lines. These findings suggest that NO synthesis may be an important mechanism in BCG-mediated anti-tumour therapy.

BCG Vaccine↗

PubMed1998

Nitric oxide synthase activity in human renal cell carcinoma.

PURPOSE: Nitric oxide (NO) is generated in mammalian tissue by the conversion of L-arginine to L-citrulline. The reaction is catalyzed by nitric oxide synthase (NOS). NO has been suggested to have a dual role in tumor biology with both antitumor and tumor promoter activity. Furthermore, it has been proposed that NO contributes to interleukin-2-induced antitumor activity. Since interleukin-2 is used in the treatment of renal cell carcinoma (RCC) it was of interest to study the NOS activity in the human kidney and in RCC and its correlation to tumor grade. Furthermore, the effect of cytokine treatment on NOS activity and the effect of NO donor application was studied in cultured cells. MATERIALS AND METHODS: The effect of cytokine treatment on NOS activity and the effect of NO donor application on cell proliferation was studied in cultured human proximal tubular cells and in RCC cell lines HN4 and HN51. NOS activity was measured by the L-arginine to L-citrulline conversion assay. RESULTS: Calcium-dependent NOS activity was found in all non-malignant kidney tissues (486+/-63 pmol. min(-1) g(-1) tissue). The activity was significantly lower in RCC (24+/-6 pmol. min(-1) g(-1) tissue) and correlated with tumor grade; thus high grade tumors showed lower activity than low grade tumors. Calcium-independent NOS activity was not detected in non-malignant kidney tissue or in RCC tissue. In cultured proximal tubular cells and RCC cell lines HN4 and HN51, cytokine treatment induced a marked increase in NOS activity and NO exerted cytostatic effects on these cell lines. CONCLUSIONS: The NOS activity was higher in non-malignant kidney tissue than in RCC tissue and was inversely correlated with tumor grade. Furthermore, cytokine treatment induced a marked increase in NOS activity and NO exerted cytostatic effects on cultured proximal tubular cells and RCC cell lines.

Analysis of Variance↗

PubMed1997

Visualisation of nitric oxide released by nerve stimulation.

We have visualised nitric oxide (NO) released from the electrically stimulated myenteric plexus and hypogastric nerve. NO was visualised by a reaction with luminol and hydrogen peroxide to generate photons which were counted using a microscope coupled to a photon counting camera. Electrical stimulation of the tissues induced an increase in photon counts which was frequency-dependent and prevented by inhibition of the NO synthase or by tetrodotoxin. The light emitted during nerve stimulation was not only observed at the nerve terminals but also at the axon and soma. Our results indicate that NO released from the whole nerve cell may affect target cells surrounding all parts of the nitrergic neuron. Thus, NO functions as a unique mechanism of synaptic and non-synaptic communication in the nervous system.

Animals↗

PubMed1997

Effects of local anaesthetics on the gross receptor potentials in the guinea pig cochlea.

Local anaesthetics have been used intravenously and intratympanally to reduce tinnitus. In order to clarify its action in the periphery, we applied 0.5 mM tetracaine in the scala tympani in 18 cochleae and studied the effects on the receptor potentials. We used a temporal bone preparation of the guinea pig ear in vitro exposing the fourth cochlear turn where the cochlear microphonics (CM) and the summating potential (SP) were recorded. The perfusion was kept at a rate of 50 microliters/min. The frequency response of the cochlea was determined at the beginning of each experiment and the responses were recorded at the best frequency of the preparation. In another five cochleae an accumulated dose-response relationship was determined by increasing the tetracaine concentration in steps (50, 100, 300, 500, 1000 and 2000 microM), measuring the difference in amplitude of the receptor potentials. The CM decreased significantly (p < 0.001; mean 0.37 mV; SD 0.29). In 12 cochleae the SP was initially positive and did not increase significantly (p = 0.16; mean 0.07 mV; SD 0.16). In six cochleae the SP was initially negative and all changed polarity to positive and increased significantly (p < 0.05; mean 0.36 mV; SD 0.28). The effects on both the CM and the SP were reversible. Owing to the inter-individual variation between the cochleae the SP/CM ratio was determined and it increased significantly (p < 0.001; mean 0.18; SD 0.11). In the accumulated dose-response experiments the CM decreased significantly (p < 0.05) in a dose-dependent way, whereas the SP did not increase significantly. The SP/CM ratio increased significantly (p < 0.05) at 300 microM and 500 microM. We hypothesize that the peripheral tinnitus-reducing action of local anaesthetics is in part due to a reversal of the SP, but also to a reduction of the CM. The difference in effect of tetracaine on the receptor potentials, the CM and the SP, suggests that the SP is not dependent on the CM.

Anesthetics, Local↗

PubMed1994

Release of nitric oxide by nerve stimulation in the human urogenital tract.

Nerve-induced release of the nitric oxide (NO) breakdown products nitrite (NO2-) and nitrate (NO3-) and the histochemical localization of NO synthase in the human penile corpus cavernosum and urethra were studied. Relaxations induced by nerve stimulation were inhibited by N omega-nitro-L-arginine methyl ester (L-NAME), an effect which was reversed by L-arginine. Relaxations elicited either by nerve stimulation or exogenous NO were accompanied by the appearance of equivalent amounts of NO2- and NO3- over a very similar time course. Nerve-induced release of NO2- and NO3- was inhibited by L-NAME. Histochemical studies showed NADPH diaphorase and NO-positive nerve fibres surrounding the arteries and smooth muscle bundles in the corpus cavernosum and the urethra. The results suggest that NO is a mediator for non-adrenergic non-cholinergic relaxation in the human urogenital tract.

Amino Acid Oxidoreductases↗

PubMed1994

Tuned phasic and tonic motile responses of isolated outer hair cells to direct mechanical stimulation of the cell body.

Guinea pig outer hair cells (OHCs) isolated from the two apical turns of the cochlea and firmly attached to a suction pipette, were subjected to the stimulus of the near-field (particle) displacements of a calibrated oscillating fluid jet aimed at the lateral cell walls. The longitudinal length changes of the OHCs in response to stimulation, in a direction orthogonal to that of the fluid jet, were recorded by a photodiode array. The response had two components; a phasic length change which followed the frequency of the particle displacement of the jet cycle by cycle, and a tonic length change which took several milliseconds to develop depending on the magnitude of the mechanical stimulus. When the hair cell changed length the lateral walls of the OHC moved in antiphase, moving apart during shortening and together during lengthening. With increased stimulus level the phasic response grew in proportion to the stimulus magnitude and began to saturate at the highest stimulus levels, while the tonic response grew in proportion to the square of the stimulus magnitude. Both the direction of the tonic length change and the phase of the phasic component could alter with the level of stimulation. Isolevel and isoresponse-frequency functions of both the tonic and phasic length changes revealed that both response types were tuned to similar resonant frequencies (RF) between 150 and 2500 Hz. The phase of the phasic length change began to lag at frequencies just below the RF, lagged by about 90 degrees at the RF and lagged by a further 90 degrees at frequencies above RF. The frequency response properties of the OHCs closely corresponded to those of a damped, forced, mechanical resonance. The tonic response disappeared and the phasic response was reduced at low-levels as a consequence of intense mechanical stimulation and with time.

Acoustic Stimulation↗

PubMed1992

The tuned displacement response of the hearing organ is generated by the outer hair cells.

The motile responses of the guinea-pig hearing organ in response to a tone applied to the ear were measured by laser interferometry. Two types of responses can be recorded: (i) a vibration at the frequency of the applied tone; and (ii) a displacement response consisting of a shift in the position of the organ surface. The purpose of this study is to characterize the displacement response. The results are as follows. There is a relationship between the frequency of highest sensitivity (best-frequency) of the displacement response and the site from which it is recorded. High best-frequencies are noticed at more basal locations, low best-frequencies towards the apex. The displacement response is more frequency-selective than the vibration response. The displacement response is observed within physiological sound pressure levels. Its sharpness is dependent on the stimulus intensity, it shows biological variability and can be manipulated by drugs that are known to modify the receptor potential of the sensory cells, or to interfere with outer hair cell motility. These results suggest that the displacement response is an important step in the transduction process in the mammalian hearing organ and that it is generated by the motile action of the outer hair cells.

Acoustic Stimulation↗

PubMed1992

Sound induced displacement response of the guinea pig hearing organ and its relation to the cochlear potentials.

The sound induced motion of the cells within the fourth turn of the guinea pig organ of Corti was studied in an in vitro preparation (Ulfendahl et al. 1989). The cells were visualised by relief microscopy, achieved by an oblique illumination technique. The motion of the sensory cells was observed during the recording of the extracellular receptor potentials; the cochlear microphonics (CM) and the summating potential (SP). Our results show that the temporal bone preparation sustains an endocochlear potential and maintains the receptor potentials for 3-4 h. During the tone stimulus the outer hair cells were seen to elongate and the surface of the organ of Corti was displaced in the direction of scala vestibuli. The displacement response showed two frequency maxima, one at 150 and one at 300 Hz. The mechanical tuning of the sensory organ coincided with the tuning of the receptor potentials. Both the mechanical and the electrical responses at the 300 Hz peak were vulnerable to the administration of methylene blue suggesting cyclic GMP dependence, whereas the 150 Hz peak was unaffected. We conclude that the outer hair cells provide active tuning in the organ of Corti.

Acoustic Stimulation↗

PubMed1992

Functional and morphological comparisons between cochlear outer hair cells and muscle tissues in the guinea-pig.

The effect of polylysine on the motility of outer hair cells and various muscle types was compared. Poly-L-lysine and its stereoisomer, poly-D-lysine, inhibited acoustically induced length changes of isolated outer hair cells from the guinea-pig hearing organ. The frequency specific displacements of the hearing organ in response to a tone stimulus are also inhibited to polylysine (Brundin et al. 1991). Poly-L-lysine, and its stereoisomer, irreversibly attenuated motile responses to transmural stimulation of guinea-pig ileum, vas deferens and taenia coli in a dose dependent manner, but were without significant effect on motile responses in skeletal and heart muscle. L-lysine, D-lysine, and the negatively charged polyaminoacid poly-L-aspartate, were without significant effect on outer hair cell and smooth muscle motility. The inhibitory effect of polylysine in smooth muscle is a direct effect on the muscle cell since polylysine attenuated acetylcholine- and adenosine triphosphate-induced contractions in the ileum, and ATP- or noradrenaline-induced contractions in the vas deferens. Pillar structures, believed to be of importance to excitation contraction coupling, were compared. In heart and skeletal muscle the pillars span the gap between sarcoplasmic reticulum and T-tubuli, deeply recessed into the muscle cell. In smooth muscle and outer hair cell the pillars are in closer relation to the cell exterior. The length of the pillars of the outer hair cells exceeds by two times that of smooth and skeletal muscle. The susceptibility of outer hair cells and smooth muscle tissue to the positively charged polylysine may indicate similarities in membrane or channel composition.

Animals↗

PubMed1991

Frequency-specific position shift in the guinea pig organ of Corti.

The organ of hearing is tuned as expressed both in the vibratory response of the cochlear partition and in the resulting receptor potentials of the sensory cells. We now demonstrate a sharply tuned response, consisting of a position shift of the surface of the organ of Corti, occurring during the presentation of a tone. The magnitude of the position shift exceeds that of the vibratory response to the stimulus. The shift is most pronounced in the region of the outer hair cells, and its affected by an inhibitor of outer hair cell motility. We conclude that the response is induced by the action of the outer hair cells.

Acoustic Stimulation↗

PubMed1991

Mechanically induced length changes of isolated outer hair cells are metabolically dependent.

Isolated outer hair cells from the organ of Corti of the guinea pig have been shown to change length in response to a mechanical stimulus in the form of a tone burst at a fixed frequency of 200 Hz (Canlon et al., 1988). In the present study, the threshold of movement for individual outer hair cells is related to the original length of the cell such that long cells are more sensitive than short cells for all cochlear locations studied. Length changes could be elicited when the stimulus was projected at any site along the longitudinal axis of the plasma membrane. Length changes were not elicited when the stereocilia were stimulated directly. These mechanically-induced length changes were found to be metabolically dependent. In the presence of either sodium cyanide or 2,4-dinitrophenol, the motile response of outer hair cells was completely blocked within 30 min. When the extracellular pH was altered in a graded fashion, the motile response decreased gradually. Furthermore, 3 microM poly-L-lysine or poly-D-lysine of different molecular weights were also effective in blocking the motile response, whereas the negatively charged polyaminoacid, poly-L-aspartate, was not effective. Fluorescently-labelled poly-lysine demonstrated that the plasma membrane, stereocilia, and nucleus were the most intensely stained structures of the outer hair cells. It is suggested that the passive influx of poly-lysine is responsible for the inhibition of the motile response. Finally, the finding that the bidirectional motile response of isolated outer hair cells induced by mechanical stimulation is dependent on the metabolic state of the cell distinguishes this type of motility from the electrically induced outer hair cell shape changes.

2,4-Dinitrophenol↗